B3P2 - Mobile and nomadic communications Flashcards
ad hoc mode (WiFi)
where all devices can directly message one other in a WiFi-net;
bipolar
where 1s and 0s and repped by +1 and -1 amplitudes;
channel bonding
merging 2+ channels for to get widerBandwidth;
channel equalisation (refSig)
where referenceSignals are used to check distortion;
channelisation (chip) code
where orthogonal chipCodes are used to distinguish simultaneously transmitted dataStreams;
chip
bipolarValues of fixedDuration concatenated to rep a 1 or 0;
correlation
where a signal is extracted from other signals;
cyclic prefix
where the last part of a symbol is copied and pasted to the start of the symbol, thereby protecting against inter-symbol interference;
delay spread
the waiting time for all zig-zags of a multipathSignal to arrive;
dynamic frequency selection (DFS) [radar]
where the device switches to a different channel if radar is detected in a 5MHz unlicensedBand;
fast link adaptation
adapting codeRates and modMethods to mobileComm conditions;
frequency division multiplexing (FDD)
where separate frequencyBands are used for uplink and downlink;
guard band
where an interval of spectrum is left unused to prevent interference between neighbouring bands;
high-speed packet access (HSPA)
uses 15 different 16-chipCodes allocated dynamically to users in WCDMA and 3G;
infrastructure mode
where all devices message via the accessPoint in a WiFi-network;
maximum transmission rate
the max numUsefulBits that can be transmitted into the channel using the highest codeRate;
OFDM symbol period
T_OFDM = T_us + T_cp;
orthogonal frequency division multple access (OFDMA)
where users are allocated groups of subchannels each;
orthogonal frequency division multiplexing (OFDM)
where closelySpaced subcarriers of signals orthogonally overlap;
orhogonal variable speading factor (OVSF)
= chipCodes = channelisationCodes;
pilot signal (ref)
reference signals used for distortionCorrection or scheduling;
power control (govReg)
baseStationRegs on deviceTransmissionPower in a cell;
processing gain (ratio)
spreadBandwidth / unspreadBandwidth;
pseudo-random code (pseudo-noise code)
a scrambling-noise code in WCDMA;
resource element
a singleSymbol in a singleSubchannel in a resourceBlock;
scheduling
the dynamicAllocation of commResources to users;
scrambling code
a noise-random-like chipSequence;
single-carrier frequency division multiple access (SC-FDMA)
where a symbol is duplicated across all subcarriers in a userResourceAllocation in the uplink in 4G;
slot
the fixedDuration of a resource Block = 0.5 ms in 4G;
spreading (chip) code
= chipCode = channelisationCode;
spreading factor
= numChips in chipCode because chipDuration is fixed;
spread-spectrum transmission
where mod-signal is given widerBandwidth to get greater resistance to noise;
subcarrier (OFDM)
oneOfThe carrierWaves comprising the OFDM signal;
subchannel (OFDM)
isCentredOn and contains subcarrierWave in OFDM;
time division du/multiplexing
where a frequencyBand is shared through rapidly alternatingSlots;
Transmit Power Control (TPC)
a 5MHzUnlicensedBand protocol where accessPoint sets maxPower for eachDevice;
wideband code division multiple access (WCDMA)
where chipCodes enable dataStreams to be transmitted simultaneously over a channel in 3G;
wireless local area network (WLAN)
= WiFi net;
