16ary Quadrature Amplitude Modulation (16-QAM), one of the forms of QAM, is a modulation scheme. In QAM, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are possible. In digital telecommunications as the data is usually binary, the number of points in the grid is usually a power of 2 (2,4,8...). As QAM is usually square, the most common forms of QAM are 16-QAM, 64-QAM, 128-QAM and 256-QAM. By moving to a higher-order constellation, it is possible to transmit more bits per symbol. However, if the mean energy of the constellation is to remain the same (by way of making a fair comparison), the points must be closer together and are thus more susceptible to noise and other corruption; this results in a higher bit-error rate and so higher-order QAM can deliver more data less reliably than lower-order QAM.
Absorption Spectrum is a diagram which shows the wavelengths of electromagnetic radiation absorbed by a material. The material could be a gas, a solute or a solid. An absorption spectrum is, in a sense, the inverse of an emission spectrum.
Adaptive Equaliser is a channel equaliser whose parameters are updated automatically and adaptively during the transmission of data. These equalizers are commonly used in fading channels to improve transmission performance.
Adaptive power control is a technique employed by wireless infrastructure systems that lowers the power of a signal in a cell site whenever the site detects that the user's phone is close to the source of the signal. This saves power in the phone, and thus saving battery life too.
Adaptive Differential Pulse Code Modulation(ADPCM) is the process by which analog voice samples are encoded into high-quality digital signals. The first ADPCM standardised by the CCITT is G.721 for 32 kbps. Later came the standards G.726 and G.727 for 40, 32, 24 and 16 kbps. ADPCM is used to send sound on fiber-optic long-distance lines as well as to store sound along with text, images and code on a CD-ROM.
Automatic Gain Control (AGC) is a system which controls the gain of a signal. Using AGC means that weaker signals receive more gain and srongers signals receive less gain or none at all.
Access Grant Channe l(AGCH) is a downlink control channel used in GSM systems to assign mobiles to a Stand-alone Dedicated Control Channel (SDCCH) for initial assignment.
Assisted Global Positioning System (AGPS) is a method used for determining mobile station (MS) location in terms of universal latitude and longitude co-ordinates. This capability has been mandated for wireless carriers in the United States by the Federal Communication Commission, so emergency callers can be easily located in times of crisis. AGPS implies that the mobile not only has GPS hardware and software but that the wireless network is providing the mobile with short assistance messages.
Amplifier, or electronic amplifier, is commonly used in radio and television transmitters and receivers, high-fidelity ("hi-fi") stereo equipment, microcomputers and other electronic digital equipment, guitars and other instrument amplifiers.
Advanced Multi-Rate Codec (AMR) is a speech codec standardised by ETSI for GSM. The codec adapts its bit-rate allocation between speech and channel coding, thereby optimising speech quality in various radio channel conditions. For this reason, 3GPP (under which the next stage GSM speech quality will be realised) has selected the AMR codec as an essential speech codec for the next generation system.
Analog system uses an analog transmission method to send voice, video and data-using analog signals, such as electricity or sound waves, that are continuously variable rather than discreet units as in digital transmissions. Mobile analog systems include AMPS, NMT and ETACS.
Analog Transmission refers to analog signals propagated over various media as continuously varying electromagnetic waves.
Automatic Power Control (APC) is a technique of measuring the performance of a radio channel and adjusting the power of the transmitter to a level appropriate for link characteristics.
Adaptive Pulse Code Modulation (APCM) is a technique used to share occupied bandwidth among a maximum number of subscribers during peak times by reducing the signal sampling rates of each subscriber.
Application Support (APS) is a sublayer in the ZigBee protocol stack. The responsibilities of the APS sub-layer include maintaining tables for binding to match two devices together based on their services and their needs, and forwarding messages between bound devices. The APS sub-layer is also responsible for determining the responsibilities of the ZDO, to initiate/respond to binding requests and to establish a secure relationship between network devices.
Attenuator is a device specifically designed to decrease the magnitude of a signal transmitted through it.
Average power is the peak power averaged over time and is usually applied to pulsed systems where the carrier power is switched on and off.
Band in telecommunication refers to the following definitions: 1. The range of frequencies between two defined limits which are used for a specific purpose. 2. One of the geo-political boundaries established to define a WATS (Wide Area Telephone Service) serving area.
Band Elimination Filter is an electrical device which blocks a receiving unit from recognising a specific range of frequencies.
Band Pass Filter is a radio wave filter that passes frequencies within a certain range and rejects frequencies outside that range. A Resistor-inductor-capacitor circuit is an example of Band Pass Filter.
Baseband is the transmission of a digital or analog signal, signaling at its original frequencies and in its original form. It should not be changed by modulation.
Baseband Layer, also known as Baseband Packet, is a physical layer protocol in the Bluetooth protocol stack. The Baseband in the Bluetooth not only manages physical channels and links but also other services such as error correction, data whitening, hop selection and Bluetooth security. The Baseband layer lies on top of the Bluetooth radio layer in the bluetooth stack. The Baseband protocol is implemented by a Link Controller, which works with the Link Manager by carrying out link level routines such as link connection and power control. The Baseband also manages asynchronous and synchronous links, handles packets, does paging and enquiry to access and find Bluetooth devices in the area.
Baseband signal is a signal with frequency content centered around DC. Typically it is the modulating signal for an RF carrier.
Bent pipe technology is a satellite technology to transmit calls from one point on Earth to a satellite and back down to another point.
Breakout Gateway Control Function (BGCF), a component in the IP Multimedia Subsystem (IMS), controls call transfers to and from the Public Switched Telephone Network (PSTN).
Common Air Interface (CAI) is a set of open standards describing the physical and logical characteristics of a link between a Base Station and a Mobile Station. These standards are used by infrastructure and handset manufactures to design and build equipment that is capable of inter-operating with each other's systems.
Call Diversion is the feature used to divert incoming calls on a mobile phone to any other telephone or to a Mailbox/Combox on a GSM system.
Carrier means the continuous frequency capable of being modulated or impressed with a second signal.
Carrier Frequency refers to the nominal frequency of a carrier wave, the frequency of the unmodulated electrical wave at the output of an amplitude modulated, the centre frequency of a frequency modulation signal, frequency modulated or phase modulated transmitter of the output of a transmitter when the modulation is zero.
Co-channel interference (CCI) refers to interference from 2 different radio stations on the same frequency. CCI is one of the major limitations in cellular and PCS wireless telephone networks. In the case of TDMA networks, such as GSM/GPRS or NADC (otherwise known as "IS-136"), the co-channel interference is mainly caused by the spectrum allocated for the system being reused multiple times ("frequency reuse"). Co-channel interference, when not minimised, decreases the ratio of carrier to interference powers (C/I) at the periphery of cells, causing diminished system capacity, more frequent handoffs and dropped calls.
CCITT is the abreviation of the International Telegraph and Telephone Consultative Committee in France. CCITT is a standards body based in Geneva that publishes "recommendations" on standards used worldwide throughout the communications industry.
Code Division Multiplexing or Code Division Multiplex (CDM) is a technique in which each channel transmits its bits as a coded channel-specific sequence of pulses. This coded transmission typically is accomplished by transmitting a unique time-dependent series of short pulses, which are placed within chip times within the larger bit time. All channels, each with a different code, can be transmitted on the same fibre and asynchronously demultiplxed. Other widely used multiple access techniques are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA).
Chase Combining (CC), also known as Convolution Code, is one of the two fundamental forms of Hybrid ARQ (HARQ). The other one is Incremental Redundancy (IR). In Chase Combining, each re-transmission repeats the first transmission or part of it. While Chase Combining is sufficient to make AMC robust, IR offers the potential for better performance with high initial code rates and FER operating points at the cost of additional memory and decoding complexity.
Enhanced or extended TDMA (E-TDMA) is an enhanced version of TDMA which will not only serve cellular, but could provide PCN-like services within current spectrum allocations.
Enhanced Full Rate is a voice coding algorithm applied in PCS-1900 systems (and now in GSM-900 as well. The first system was installed in Hong Kong).
Electromagnetic Spectrum refers to the full range of electromagnetic frequencies, which includes Radio Frequency (RF).
Encoder is a converter used to create a specific addressed message.
EPOC, now called Symbian OS, is an operating system optimised for mobile phone/PDA uses. It was developed by Symbian which is a joint company of Psion, Nokia, Ericsson, Motorola and Matsushita (Panasonic). EPOC turns voice-oriented handsets into Mediaphones and Wireless Information Devices. EPOC places a lighter load on the processor compared to present PDA operating systems and therefore has the capacity to enhance the multimedia capacity of mobile phones.
Equalisation is a technique often used in mobile wireless communications to compensate for communication channel distortions.
European Radio Messaging System is a paging system used in Europe and other parts of the world.
Error correction is the process of correcting errors in data transmitted over a radio channel using Forward Error Correction (FEC) techniques.
Error probability is a computation of the likelihood of an error involving the Probability Density Function (PDF).
The error vector is the vector difference between a reference signal and a measured signal and is a complex quantity containing a magnitude and phase component.
Eye diagram is a superposition of segments of a received PAM signal displayed on an oscilloscope or similar instrument. The eye diagram is used to assess impairments in the radio channel.
Fast Associated Control Channel (FACCH) is the channel derived by pre-empting information in a traffic channel. It is used to send handoff and similar messages.
Fading is the variation in signal strength from its normal value. Fading is normally negative and can be either fast or slow. It is normally characterised by the distribution of fades, Gaussian, Rician, or Rayleigh.
Fast Access Station Switching (FASS), a concept in the WiMAX network, is a method by which an MS can change its access station from frame to frame depending on the station selection mechanism. The access station can be an RS, BS, or MMRBS. The MS refers to transmitting/receiving data to/from one of the active stations (the anchor station) during any given frame.
Fast Base Station Switching (FBSS), defined in the IEEE 802.16-2005 (mobile WiMAX) network, is a method to allow switching between any type of access station such as RS, BS, or MMR-BS). Switching can occur between the same or different type of access stations.
Federal Communications Commission (FCC) is the regulatory body governing communication technologies in the US. Established by the Communications Act of 1934, as amended, it regulates interstate communications (wire, radio, telephone, telegraph and telecommunications) originating in the United States.
Fast Fourier Transform (FFT) is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse. FFTs are of great importance to a wide variety of applications, from digital signal processing to solving partial differential equations and to algorithms for quickly multiplying large integers.
Frequency Hopping (FH) is a periodic changing of frequency or frequency set associated with transmission. It is a sequence of modulated pulses with a pseudo-random selection of carrier frequencies.
Frequency Hopping Multiple Access (FHMA) is a digital technology used in Geotek Communications Inc.'s specialised mobile radio network.
Frequency Hopped Spread Spectrum (FHSS) is a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudo-random sequence known to both transmitter and receiver. It is used in WLAN 802.11 physical layer.
Fixed WiMax refers to the fixed wireless broadband services as defined by the IEEE 802.16d (also known as IEEE 802.16-2004). IEEE 802.16d product profile utilises the OFDM 256-FFT (Fast Fourier Transform) system profile. The Fixed WiMAX 802.16-2004 standard supports both Time Division Duplex (TDD) and Frequency Division Duplex (FDD) services -- the latter of which delivers full duplex transmission on the same signal if desired. The mobility features of WiMax are defined in IEEE 802.16e (or 802.16-2005).
Flat fading is a type of fading in a communications channel that attenuates or fades all frequencies in the channel by the same amount.
Frequency Modulation (FM) is a form of angle modulation in which the instantaneous frequency of a sine-wave carrier is caused to depart from the carrier frequency by an amount proportional to the instantaneous value of the modulating wave. In FM, signals of different frequencies represent different data values.
Forward Channel is used by the base station to communicate with a mobile station.
In radio communications, a forward link is the link from a fixed location (e.g., a base station) to a mobile user. If the link includes a communications relay satellite, the forward link will consist of both an uplink (base station to satellite) and a downlink (satellite to mobile user).
Frequency diversity is the simultaneous use of multiple frequencies to transmit information. This is a technique used to overcome the effects of multipath fading since the wavelength for different frequencies result in different and uncorrelated fading characteristics.
Frequency reuse is a technique of reusing frequencies and channels within a communications system to improve capacity and spectral efficiency. Frequency reuse is one of the fundamental concepts on which commercial wireless systems are based that involves the partitioning of an RF radiating area (cell) into segments of a cell. One segment of the cell uses a frequency that is far enough away from the frequency in the bordering segment that it does not provide interference problems. Frequency re-use in mobile cellular systems means that each cell has a frequency that is far enough away from the frequency in the bordering cell that it does not provide interference problems. The same frequency is used at least two cells apart from each other. This practice enables cellular providers to have many times more customers for a given site licence.
Frequency selective fading is a type of signal fading occurring over a small group of frequencies caused by a strong multipath component at those frequencies.
Full rate refers to voice codecs in a communications system. Most frame formats are designed to accommodate full and half-rate channels, with the intention of implementing half-rate coding as the technology permits to double the capacity of the system. The full-rate codec uses all of the time-slots available.
Gaussian channel is an RF communications channel which has the properties of a wide-band uniform noise spectral density resulting in a random distribution of errors in the channel.
Geo-stationary Earth Orbit Systems (GEOS) is a communications system with satellites in geo-synchronous orbits -- 22,300 miles above the Earth.
Gi interface is the reference point between a GPRS network and an external packet data network.
Geographical Information System (GIS) refers to a computer system capable of capturing, storing, analysing, and displaying geographically referenced information, that is data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel and spatial data that go into the system.
GPRS Tunnelling Protocol (GTP) is a protocol used by the GPRS backbone network for packet switching. GTP is a protocol defined on both the Gn and Gp interfaces between GSNs in a GPRS network.
Ground Station, also called a downlink station, refers to the collection of communications equipment designed to receive signals from (and usually transmit signals to) satellites.
GTP Tunnel is used to communicate between an external packet data network and a mobile station in a GPRS network. A GTP tunnel is referenced by an identifier called a TID and is defined by two associated PDP contexts residing in different GSNs. A tunnel is created whenever an SGSN sends a Create PDP Context Request in a GPRS network.
Half rate is a term used in voice codecs in a communications system. Most frame formats are designed to accommodate full and half-rate channels, with the intention of implementing half-rate coding as the technology permits to double system capacity. The half rate codec uses only half of the time-slots in the frame.
Handheld Device Markup Language (HDML) Specifications allow Internet access from wireless devices such as handheld personal computers and smart phones. This language is derived from HyperText Markup Language (HTML).
Handheld Device Transport Protocol (HDTP) is optimised for HDML. It presents the HDML to the HDML interpreter in an appropriate format.
The hidden node problem occurs in wireless networking when a node is visible from a wireless hub, but not from other nodes communicating with said hub. This leads to difficulties in media access control. Hidden nodes in a wireless network refer to nodes which are out of range of other nodes or a collection of nodes. Take a physical star topology with an Access Point with many nodes surrounding it in a circular fashion; each node is within the communication range of the Access Point, however, not each node can communicate with each other.
HomeRF is a networking standard for home wireless communication, which is a competitor to Wi-Fi that integrates voice, data, and streaming media into a single wireless signal.
Hybrid Phase Shift Keying (HPSK), also known as Orthogonal Complex Quadrature Phase Shift Keying (OCQPSK), is the spreading technique used in the reverse link of 3G systems to reduce the peak-to-average ratio of the signal by reducing zero crossings and 0 degree phase transitions.
High Rate/Direct Sequence Spread Spectrum Physical Layer (HR/DSSS PHY) is the enhanced physical layer defined by IEEE 802.11b which supports data transfer at up to 11 Mbps. Unlike the earlier versions of IEEE 802.11 which supported data rates of up to 2 Mbps, HR/DSSS uses complementary code keying which divides the chip stream into a number of 8-bit code symbols.
Hertz (Hz) is a measurement of frequency in cycles per second. One Hertz is one cycle per second.
The International Mobile Equipment Identity (IMEI) is a number unique to every GSM and UMTS mobile phone. It is usually found printed on the phone underneath the battery and can also be found by dialling the sequence *#06# into the phone. The IMEI number is used by the GSM network to identify valid devices and therefore can be used to stop a stolen phone from accessing the network. For example, if a mobile phone is stolen, the owner can call his or her network provider and instruct them to "ban" the phone using its IMEI number. This renders the phone useless, regardless of whether the phone's SIM is changed.
IP Multimedia Private Identity (IMPI) is one of the two identities used by an IP Multimedia Subsystem (IMS). The other one is the IP Multimedia Public Identity (IMPU). Neither are phone numbers or other series of digits, but URIs, that can be digits (a tel-uri, like tel:+1-555-123-4567) or alphanumeric identifiers (a sip-uri, like sip:email@example.com). The IMPI is unique to the phone, and you can have multiple IMPU per IMPI (often a tel-uri and a sip-uri). The IMPU can also be shared with another phone, so both can be reached with the same identity (for example, a single phone-number for an entire family).
Interference is the effect that occurs when undesired signals inhibits or degrades the reception of a desired signal.
Incremental redundancy (IR) is the feature used by EDGE (EGPRS) systems to get maximum performance out of the available bandwidth. It works by first sending only the minimum amount of redundant data, i.e. in most cases, no redundant data. If the data is not decoded properly, the system will resend the same data using a different puncture or coding scheme, increasing the amount of redundant data and the likelihood of recovering from the errors. If data is re-transmitted using a different puncture or coding scheme, it is then re-combined with the first transmission to increase redundancy.
JavaPhone is a Java API specification controlling contacts, power management, call control and phone book management. It is intended specifically for the programming requirements of mobile phones.
Japanese Total Access Communication System (JTAGS) is a 1G technology deployed in Japan based on the European TACS system. JTAGS is operating in the 900 MHz band.
Ka-Band refers to the bandwidth of electromagnetic waves between 33 GHz to 36 GHz, which is primarily used in satellites operating at 30 GHz uplink and 20 GHz downlink for mobile voice communications.
Key-pulse signal is the first signal in a multi-frequency outpulsing format. It is a control signal used to prepare the remote customer installation to receive digits.
1 kHz (KiloHertz) is equal to 1,000 Hertz, which is a measurement of frequency.
Kpbs (Kilobits per second) is a measurement of data rate, for example, data services for 2G operates at maximum speed of 9.6 Kbps.
Ku-Band refers to the bandwidth of an electromagnetic wave between 12 GHz to 14 GHz. It is primarily used in satellites operating at 14 GHz uplink and 11 GHz downlink in supporting broadband TV and Direct Broadcast Satellite (DBS) system (DSS).
Logical Link Control and Adaptation Protocol, typically short as L2CAP, is used within the Bluetooth protocol stack at the data link layer. It passes packets to either the Host Controller Interface (HCI) or on a hostless system, directly to the Link Manager.
A Low-Density-Parity-Check code (LDPC code) is an error-correcting code and a method of transmitting a message over a noisy transmission channel. While LDPC and other error correcting codes cannot guarantee perfect transmission, the probability of lost information can be made as small as desired. LDPC was the first code to allow data transmission rates close to the theoretical maximum, the Shannon Limit.
Lightweight Extensible Authentication Protocol (LEAP), also known as Cisco-Wireless EAP, is a Cisco security technology that builds on Wi-Fi's WEP encryption. It changes the WEP key dynamically during a session to make it less likely that a snooper will be able to derive the key. LEAP provides username/password-based authentication between a wireless client and a RADIUS server like Cisco ACS or Interlink AAA. LEAP is one of several protocols used with the IEEE 802.1X standard for LAN port access control.
Location Server allows end-users to connect real-time location information from mobile service operators with mapping and routing information. Location server enables mobile service providers to provide their end-users with personalised content that is location-dependent.
Linear Power Amplifier (LPA) is the final amplification stage in a multicarrier transmitter that has been designed and optimised to produce a linear response. By operating in the linear mode, the amplifier reduces the non-linear effects that produce intermodulation products and side-lobe spectra that cause adjacent channel interference.
Linear Predictive Coding (LPC) is a speech encoding scheme that uses periodic pulses to excite a filter, similar to the way human voice is produced. The code is predictive in that it uses knowledge of past data (represented as vectors) to predict future values in a feed forward manner.
Least Significant Bit (LSB), in a binary coding scheme, is the bit having the least numerical value. Analogous to the units position in a decimal number.
M-law companding is a type of non-linear (logarithmic) quantising, companding and encoding technique for speech signals based on the m-law. This type of companding uses an m factor of 255 and is optimised to provide a good signal-to-quantising noise ratio over a wide dynamic range.
Multiple Access Interference (MAI) is a type of interference caused by multiple cellular users who are using the same frequency allocation at the same time. In both 2G and 3G moble networking, each user is then given a pair of frequencies (uplink and downlink) and a time frame slot. Different users can use the same frequency in the same cell except that they must transmit at different times. This multiple-access interference can present a significant problem if the power level of the desired signal is significantly lower (due to distance) than the power level of the interfering user.
Media Gateway Control Function (MGCF), a component in the IP Multimedia Subsystem (IMS), communicates with the Call Session Control Function (CSCF) and controls the connections for media channels in an IMS-MGW. It performs protocol conversion between ISDN User Part (ISUP) and the IMS call-control protocols.
Microcell is a very small cell used in densely populated areas where traffic volume is high. There is no official definition of what cell radius distinguishes a small cell from a microcell.
Microwave is the electromagnetic wave in the frequency range of 1 to 30 GHz. Microwave-based networks are an evolving technology gaining favour due to high bandwidth and relatively low cost.
Mobile Identification Number (MIN) is a unique identification number given to a mobile unit. In most cases, this number is the telephone number of the handset. In the case of analog cellular, the MIN is used to route the call. In most second generation systems, the system assigns temporary numbers to the handset to route calls as a security precaution. See also TMSI.
Mobile Media Mode (MMM also marketed as WWW:MMM), is a marketing icon comprising a unifying industry-wide marketing symbol representing web-based mobile products and services.
Mobile IP is the key protocol to enable mobile computing and networking. It brings together two of the world's most powerful technologies -- the Internet and mobile communication. In Mobile IP, two IP addresses are provided for each computer: a home IP address which is fixed and care-of IP address which chnges as the computer moves. When the mobile moves to a new location, it must send its new address to an agent at home so that the agent can tunnel all communications to its new address.
Modulate refers to varying the amplitude, frequency or phase of a radio signal in order to transmit information.
Modulation refers to carrying information on a signal by varying one or more of the signal's basic characteristics -- frequency, amplitude and phase. Different modulation carries the information as the change from the immediately preceding state rather than the absolute state.
Metropolitan Statistical Area (MSA) is a geographic area over which a cellular operator is licenced to provide service. MSAs are groups of counties in metropolitan areas having common financial, commercial and economic ties and were first used to licence cellular services in the early '80s. MSAs cross state lines in some instances. MSAs were first used by the Dept.of Commerce to collect economic data.
Multipath is a propagation phenomenon characterised by the arrival of multiple versions of the same signal from different locations shifted in time due to having taken different transmission paths of varying lengths.
Near Field Communication (NFC) is a short-range wireless connectivity standard, jointly developed by Philips and Sony, that uses magnetic field induction to enable communications between devices when they're touched together, or brought within a few centimeters of each other. The standard specifies a way for the devices to establish a peer-to-peer (P2P) network to exchange data.
Nyquist filter is an ideal low pass filter with a cut-off frequency equal to the sampling rate. This technique is used to convert PAM pulses to an analog signal in D/A converters.
Nyquist rate is the minimum sampling rate proposed by Nyquist for converting a band limited waveform to digital pulses. The rate must be at least twice the highest frequency of interest in the waveform being sampled.
Orthogonal Frequency Division Multiplexing (OFDM) is an FDM modulation technique for transmitting large amounts of digital data over a radio wave. OFDM works by splitting the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. 802.11a WLAN, 802.16 (WiMAX) technologies use OFDM as the physical layer communication standard.
Orthogonal Frequency Division Multiple Access (OFDMA), also referred to as Multiuser-OFDM, is being considered as a modulation and multiple access method for 4th generation wireless networks. OFDMA is an extension of Orthogonal Frequency Division Multiplexing (OFDM), which is currently the modulation of choice for high speed data access systems such as IEEE 802.11a/g wireless LAN (WiFi) and IEEE 802.16a/d/e wireless broadband access systems (WiMAX).
Offset Quadrature Phase Shift Keying (OQPSK), sometimes called Staggered QPSK (SQPSK), is a type of QPSK modulation that offsets the bit streams on the I and Q channels by a half bit. This reduces amplitude fluctuations and helps improve spectral efficiency. In other words, using OQPSK increases the temporal efficiency of normal QPSK.
Output Radio Frequency Spectrum (ORFS) is a measurement for GSM signals that tests for interference in the adjacent frequency channels (ARFCNs) and results from two effects: modulation within the bursts and the power that ramps up and down, or switching transients. ORFS is a critical GSM transmitter measurement.
Orthogonal Variable Spreading Function (OVSF) is a set of spreading codes derived from a tree-structured set of orthogonal codes and are used to channelise the IMT-2000/ULTRA system.
Personal Access Communications System (PACS) is a low mobility low power wireless system designed for residential use.
Paging refers to the delivery of a message to someone when their location is unknown through a wireless device usually known as a pager.
Pulse Amplitude Modulation (PAM) is a form of signal modulation in which the data is encoded in the amplitude of a series, or train, of regularly recurrent signal pulses. PAM is used less frequently than PCM (Pulse-Code Modulation).
Paring is the process of engaging two Bluetooth devices to each other so they can communicate.
Parity is a simple error detection scheme. The method usually involves counting the '1' bits in a codeword and then setting an additional bit to either '1' or '0' depending on whether the original number of '1' bits was even or odd.
Pulse Code Modulation (PCM) is the most predominant type of digital modulation in use today. PCM performs an analog to digital conversion of the speech waveform through a sampling process and encodes and transmits the samples in a serial bit stream as 8-bit digital words.
The Packet Control Unit (PCU) is a late addition to the GSM standard. It performs some of the processing tasks of the Base Station Controller (BSC), but for packet data. The allocation of channels between voice and data is controlled by the base station, but once a channel is allocated to the PCU, the PCU takes full control over that channel. The PCU can be built into the base station, built into the BSC, or even in some proposed architectures, it can be at the SGSN site.
Peak power is the maximum instantaneous power radiated by a pulsed or bursted transmitter. It is the power radiated while the transmitter is keyed or operated.
Packed Encoding Rules (PER) is a set of rules that specifies how ASN.1-defined information is encoded when transmitted and how it is decoded when received. PER is a successor to the Basic Encoding Rules (BER). It is more efficient in terms of the number of bytes transmitted and the size of the generated encoder and decoder.
Generally speaking, phase is the current position in the cycle of something that changes cyclically.
Phase Modulation (PM) is the scheme of modulation that the phase of the carrier signal is modulated in accordance with the message signal. Paging Message Processor (PMP) is a Radio Paging Terminal or equivalent message processing system.
Phase jitter is the amount of uncertainty introduced in digital demodulation caused by the rapid fluctuation of the frequency of the transmitted signal, typically due to imperfections in the clock recovery timing.
Personal Identification Number (PIN) is a code used for all GSM-based phones to establish authorisation for access to certain functions or information. The PIN code is delivered together with your subscription.
Private Mobile Radio (PMR) is for use within a defined user group such as the emergency services or by the employees of a mining project.
Power control is a technique for managing the transmit power in base stations and mobiles to a minimum level needed for proper performance. Downlink power control applies to base stations and uplink power control to mobiles. Power control is used in nearly all wireless systems to manage interference, and in the case of mobiles, to extend battery life.
Q-Band, also known as V-Band, is a radio bandwidth range between 40 GHz t0 50 GHz.
Quadrature Amplitude Modulation (QAM) is a type of modulation where the signalling information is carried in the phase and amplitude of the modulated carrier wave. Specifically for QAM, the amplitude of two waves, 90 degrees out-of-phase with each other (in quadrature) are changed (modulated or keyed) to represent the data signal, in which each combination of phase and amplitude represents one of sixteen four-bit patterns.
Quarter CIF (QCIF) is a video image format which employs 176 horizontal pixels and 144 vertical lines. Although resolution is courser than CIF, QCIF consumes less memory while still achieving an acceptable level of clarity on small displays such as those incorporated in mobile phones.
The quadrature phase channel in a phase shift keyed system having more that 2 phase states.
Quantising is the process of assigning values to waveform samples by comparing the samples to discrete steps.
Radio is the electromagnetic waves whose frequencies are below 3,000 GHz as defined in Article 2 of the Radio Law in general. However, in practice, radio is generally refered to as electromagnetic waves whose frequencies are between 10 kHz and 300 GHz.
Radio link refers to the equipment and transmission path (propagation channel) used to carry on communications. It includes the transmitting system, the propagation channel and receiving system.
Radio port is a unit that supports transmission of signals over the air interface.
Rake receiver is a radio receiver with multiple "fingers" and utilising off-sets of a common spreading code to receive and combine several multipath (time delayed) signals. In effect using "time diversity" to overcome deep fades.
Reed-Solomon codes are block-based error correcting codes with a wide range of applications in digital communications and storage. Reed-Solomon codes are used to correct errors in many systems including: (1) Storage devices (including tape, Compact Disk, DVD, barcodes, etc) (2) Wireless or mobile communications (including cellular telephones, microwave links, etc) (3) Satellite communications. (4) Digital television / DVB. (5) High-speed modems such as ADSL, cDSL, etc.
Reflection is a process that occurs when a propagating electromagnetic wave impinges upon an obstruction whose dimensions are very large when compared to the wavelength. Reflections from the surface of the earth and from buildings or walls produce reflected waves which may interfere constructively or destructively at the receiver.
ReFLEX is a two-way paging protocol developed by Motorola for enhanced paging services. ReFLEX 25 supports outbound transfer rates of up to 6,400 bps in a 25 kHz channel and 12,800 bps in a 50 kHz channel.
Remote Access Point, also known as relay access points, is one of a number of secondary access points in a wireless network that uses Wireless Distribution System (WDS) to extend its range. Remote access points connect to a master access point.
Reuse factor, also known as frequency reuse factor, is the number of distinct frequency sets used per cluster of cells.
In radio communications, the reverse link, also known as return link, is the link from a mobile user to a fixed base station. If the link includes a communications relay satellite, the reverse link will consist of both an uplink (mobile station to satellite) and a downlink (satellite to base station).
Radio Frequency Communication (RFCOMM) is a Bluetooth protocol which is a simple set of transport protocols, providing emulated RS232 serial ports (up to sixty simultaneous connections of a bluetooth device at a time). RFCOMM is sometimes called Serial Port Emulation. The Bluetooth Serial Port Profile is based on this protocol.
Roaming refers to the movement of a mobile device from one wireless network location to another without interruption in service or loss in connectivity. When a call is made to a roaming mobile, the public telephone network will route the call to your service provider's network since that is where your phone number terminates. Your home network is then responsible for re-routing the call to the host network.
Signal-to-interference ratio (S/I) is the ratio of power in a signal to the interference power in the channel. The term is usually applied to lower frequency signals, such as voice waveforms, but can also be used to describe the carrier wave. See also carrier-to-interference ratio.
Signal-To-Noise Ratio (S/N) is a measure of the power of a signal versus noise. A higher ratio means that there is more signal relative to noise.
Sampling is the process performed in the conversion of analog waveforms to a digital format. It converts a continuous time signal into a discrete time signal or sequence of numbers.
Set-up Audio Tone (SAT) is an audio tone in the 6 kHz range added to the downlink or forward channel in analog cellular systems. The mobile detects and returns the tone. The SAT tone is used to determine channel continuity. Only one SAT tone is usually assigned to a base station or sector.
A satellite is a specialised wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth. They are used for such diverse purposes as weather forecasting, television broadcast, amateur radio communications, Internet communications and the Global Positioning System.
Satellite Communication refers to the use of orbiting satellites to relay data between multiple earth-based stations. Satellite communications offer high bandwidth and a cost that is not related to distance between earth stations, long propagation delays or broadcast capability.
Satellite Internet refers to the utilisation of telecommunications satellites in Earth orbit to provide Internet access to consumers. Satellite Internet service covers areas where DSL and cable access is unavailable. Satellite offers less network bandwidth compared to DSL or cable. The long delays required to transmit data between the satellite and the ground stations tend to create high network latency, causing a sluggish performance experience in some cases. Network applications like VOIP, VPN and online gaming may not function properly over satellite Internet connections due to these latency issues.
Satellite phone is a type of wireless mobile telecommunications system using satellites as base stations. Such systems have the ability of providing service to the oceans and other remote areas of the globe.
Scattering is a phenomenon that occurs when the medium through which a radio wave travels consists of objects with small dimensions compared to the wavelength and diffuses the wave as it propagates through it.
The Spreading Factor (SF) is the ratio of the chips to baseband information rate. Spreading factors vary from 4 to 512 in FDD UMTS. Spreading factor in dBs indicates the process gain. The lower the spreading factor the higher the data rate.
Slow Frequency Hopped Multiple Access (SFHMA) is a spread-spectrum system where the hop (dwell) time is much greater than the information symbol period. When hopping is co-ordinated with other elements in the network, the multiple access interference in the network is greatly reduced.
The Serving GPRS Support Node (SGSN) is the node which carries out the same function as the Local Agent in Mobile IP. However, an SGSN is actually considerably more complex since it also does the full set of interworking with the connected radio network. This means that the functions carried out by the SGSN vary quite considerably between GSM and UMTS.
Shadow fading is a phenomenon that occurs when a mobile moves behind an obstruction and experiences a significant reduction in signal power.
Super High Frequency (SHF) is the RF spectrum between 3 GHz and 30 GHz.
Soft Handoff (SHO) refers to two base stations -- one in the cell site where the phone is located and the other in the cell site to which the conversation is being passed, but both are held on the call until the handoff is completed. The first cell site does not cut off the conversation until it receives information that the second is maintaining the call.
Silicon-Germanium Technology (SiGe) makes it possible to design complex chips that integrate the functions of a cellular telephone, an e-mailbox and an Internet browser into a handheld information device with rapid data-transfer capability.
Signal Strength is the strength of the radio waves in a wireless network.
Silent Alert is the non-audible signal in a beeper, which discretely notifies individuals of incoming pages, typically by vibration.
Subscriber Identity Module (SIM) is a component of a Mobile System (MS) in a GSM network that contains all the subscriber information.
Subscriber Identity Module (SIM) Card is used in GSM phones to carry all critical information about the phone and subsriber.
Simulcast refers to broadcasting a message over multiple transmitters throughout a geographical region at precisely the same time.
Signal to Interference plus Noise Ratio (SINR) is the ratio of the received strength of the desired signal to the received strength of undesired signals (noise and interference).
Smart phone is a wireless phone with text and Internet capabilities. Smart phones can handle wireless phone calls, hold addresses and take voice mail. It can also access information on the Internet, send and receive e-mail and fax transmissions.
Specialised Mobile Radio (SMR) is a despatch radio and interconnect service for businesses, covering frequencies in the 220 MHz, 800 MHz and 900 MHz bands.
Signal-to-Noise + Interference Ratio (SNIR) is the ratio of usable signal being transmitted to the undesired signal (noise) plus interference from other or the same channels. It is a measure of transmission quality. The ratio of good data (signal) to bad (noise + intereference) on a line is expressed in decibels (dB).
Spectrum refers to a continuous range of frequency for electromagnetic waves.
Spectrum Allocation refers to that government designation of a range of frequencies for a category of use or uses. Allocation, typically accomplished in years-long FCC proceedings, tracks new technology development. However, the FCC can shift existing allocations to accommodate changes in spectrum demand. As an example, some UHF television channels were recently reallocated to public safety.
Spectrum Assignment refers to the government authorisation for use of specific frequencies or frequency pairs within a given allocation, usually at stated geographic locations. Mobile communication authorisations are typically granted to private users, such as oil companies, or to common carriers, such as cellular and paging operators.
Spectrum Reuse means re-applying the already assigned over-the-air spectrum to Cable TV programmes. Historically, the over-the-air spectrum has been assigned to many purposes other than that of carrying TV signals. This has resulted in an inadequate supply of spectrum to serve the needs of viewers. Cable can reuse spectrum that is sealed in its aluminum tubes.
Spectrum spreading is the process of increasing the occupied spectrum of a signal well beyond the need to transmit the information.
Speech coding is an electronic process of sampling and digitising a voice signal.
Shared Secret Data (SSD) is part of an encryption process supporting authentication of mobile phones. It uses an encryption key installed in the phone at the time of activation and known to the system through an entry in the HLR, that protects signalling and identity information. It can also be used to establish a voice privacy key.
Selective Transmit Diversity (STD) is a transmit diversity technique using multiple base stations to originate the signal and provide spatial diversity on the downlink. In STD, the transmitter selection is based on a QoS measurement made at the mobile station. See also transmit diversity, TDTD and TSTD.
Symbian is a software licencing company that develops and supplies the advanced, open, standard operating system -- Symbian OS -- for data-enabled mobile phones.
Based on XML, SyncML enables data synchronisation between mobile devices and networked services. SyncML is transport, data type and platform independent. SyncML works on a wide variety of transport protocols, including HTTP and WSP (part of WAP), and with data formats ranging from personal data (such as vCard and vCalendar) to relational data and XML documents. The SyncML consortium was set up by IBM, Nokia and Psion and is sponsored by Symbian.
Telocator Conversion Processor (TCP) is a front end processor which executes the Telocator Format Conversion (TFC) process.
Telematics means the integration of wireless communications, vehicle monitoring systems and location devices.
Temporal Key Integrity Protocol (TKIP) is part of the IEEE 802.11i encryption standard for wireless LANs security. TKIP utilises RC4 stream cipher with 128 bit key for encryption and 64 bit key for authentication. TKIP is the next generation of WEP (Wired Equivalency Protocol). TKIP provides per-packet key mixing, a message integrity check and a re-keying mechanism, thus fixing the flaws of WEP.
Transcoding refers to the operation of changing data from one format to another, such as an XML to HTML, so the output will be displayed in an appropriate manner for the device.
Transmission Frequency is the rate in Hertz at which a radio transmitter repeats a signal pattern. It is also a code number that the wireless service company assigns to represent a single frequency or set of frequencies.
Transmit Power is the amount of power used by a radio transceiver to send the signal out. Transmit power is generally measured in milliwatts, which can be converted to dBm.
Telecommunications Technology Committee (TTC) is a private-sector corporate body established in 1985 to prepare domestic standards relevant to Japanese telecommunications.
Uplink Channel Descriptor (UCD) is a concept in the IEEE 802.16 (WiMAX) network, which describes the uplink burst profile (i.e., modulation and coding combination) and preamble length for each UL burst.
UMTS Mobile Switching Centre (UMSC), a type of Mobile Switching Centre (MSC), provides UMTS 3G wireless telephony switching services and controls calls between telephone and data systems.
Universal Personal Telecommunications (UPT) is a set of standards developed by the CCITT for wireline personal communications.
Urban cells is the coverage provided by base stations located in urban areas. The radius of these cells is usually much smaller than suburban and rural cells due to the more difficult propagation environment.
V-Band, also known as Q-Band, is a radio bandwidth range between 40 GHz to 50 GHz.
Voice Activity Detector (VAD) is the device that detects voice activity and allows DTX to operate. VAD, in conjunction with DTX reduces power consumption in the mobile station and RF interference in the system by muting the transmitter when there is no voice to transmit.
VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter (see formula below). Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometers away). VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. Whilst it is more easily blocked by land features than HF and lower frequencies, it is less affected by buildings and other less substantial objects than UHF frequencies.
Viterbi algorithm is a technique for searching a decoding trellis to yield a path with the smallest distance. This is also known as maximum likelihood decoding.
Vocoder refers to a voice encoder which is a device that codes and decodes the human voice (sound waves) into digital transmission. Higher vocoder speeds offer enhanced sound quality.
Voice Activated Dialing is a feature that permits you to dial a phone number by speaking it to your wireless phone instead of punching it in yourself. The feature contributes to convenience as well as driving safety.
Voice Channel is a channel used for transmission of voice data from a base station to a cellular phone (forward voice channel) or from a cellular phone to a base station (reverse voice channel).
Voice over Wireless IP (VoWIP) is the combination of VoIP with 802.11 wireless LANs to create a wireless telephone system. VoWIP enables businesses to leverage their wireless LANs to add voice communications, enabling companies to deploy and manage voice and data over a single wireless backbone. VoWIP applications require some reservation of bandwidth to support the real-time nature of voice. Proprietary standards like Spectralink Voice Priority (SVP) are today's solution; however, the IEEE is developing the 802.11e standard for quality of service as a long-term solution.
Wireless USB (WUSB) is the wireless extension to USB (Universal Serial Bus) intended to combine the speed and security of wired technology with the ease-of-use of wireless technology. Wireless USB, based on Ultra-WideBand (UWB) defined by IEEE 802.15.3, is capable of sending 480 Mbps or even higher bandwidth at distances up to 3 meters, and 110 Mbps at up to 10 metres. It operates in the 3.1--10.6 GHz band range and spreads communications over an ultra-wideband of frequencies.