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The transmission medium is a resource that can be subdivided into individualchannels according to different criteria that depend on the technology used.Heres how the three most popular radio technologies establish channels: FDMA (Frequency Division Multiple Access)- Each user is on a different frequency- A channel is a frequency. TDMA (Time Division Multiple Access)- Each user is on a different window in time (time slot)- A channel is a specific time-slot on a specific frequency. W-CDMA (Wide-band Code Division Multiple Access)- Each user uses the same frequency all the time, but it is mixed with differentdistinguishing code patterns. A channel is a unique (set of) code pattern(s).
FDD: Frquency Division Duplexing TDD: Time Division Duplexing4
The possibility to operate in either FDD or TDD mode is allowed for efficient utilizationof the available spectrum according to the frequency allocation in different regions.FDD and TDD are defined as follows: FDDA duplex method whereby the uplink and downlink transmissions use 2 separatefrequency bands:- Uplink: 1920 MHz - 1980 MHz- Downlink: 2110 MHz - 2170 MHzEach carrier is 5 MHz wide and the uplink channel is 190 MHz away from thedownlink. So there are up to 12 pairs of carriers. TDDA duplex method whereby the uplink and downlink transmissions are carried oversame frequency using synchronized time intervals. The carrier still uses a 5 MHzband.FDD mode is the preferred mode for macro-cellular applications.TDD mode is the preferred mode for the unpaired part of the spectrum. Becauseeach time-slot can be assigned a different direction, the TDD mode offers a greatflexibility to manage duplex and asymmetric traffic. The TDD spectrum will be usedfor low mobility coverage in urban areas.
Soft Handover: Inter site handover Softer Handover: Intra site handover11
UMTS FRAMEThe UTRA/FDD Transmission is a continuous transmission. The Spreading factor hasto be chosen so that the transmission is compliant with the UMTS Frame Format.A slot is equal to 2560 chips. The number of bits per slot is variable and depends onthe Spreading Factor.A Radio Frame is equal to 15 slots, or 38.400 chips, during 10 ms. It corresponds to aprocessing time element.The System Frame Number is a counter used for a time reference in one cell. SFN value is given in the BCH (from 0 to 4095 frames).
Inner loop pc outer loop pcLocated in BTS & UE.Controls power of dedicated physical channels.Inner loop power control The base station compares the measured Eb/Nt with thecorresponding objective and the mobile station will be ordered todecrease the transmission power if the measured Eb/Nt exceeds theobjective. Otherwise, the mobile station will be ordered to increasethe transmission power. The adjustment frequency is 1500HZ.Outer loop power control Estimate Eb/Nt objective based on the measured Frame ErrorRate(FER)Eb/Nt=bit energy/density of interference power spectrum, similar to signal-to-noise ratio.