Proprietary of NTHU Communication SOC Lab, 2006 Beam Forming, Null Steering, and SDMA Selecting the weights correctly allows transmitter (receiver) to steer the energy toward a receiver (or listen in the “direction” of a transmitter). This is called beam forming In selecting the weights, transmitter can also steer energy away from unintended receivers (or not listen in the direction of interfering transmitters). This is called null steering. Beam forming can be used to extend range Null steering can be used to mitigate interference from other sectors Beam forming and null steering can be used to implement SDMA, where multiple SSs within a sector transmit/receive on the same subchannels at the same time.

Proprietary of NTHU Communication SOC Lab, 2006 Beam Forming, Null Steering, and SDMA Base Station Subscriber Beam Forming Base Station Intended Subscriber Null Steering Interfering Subscriber Base Station Subscriber 1 SDMA Subscriber 2

Proprietary of NTHU Communication SOC Lab, 2006 Channel Rejection Measured by setting transmitting power 3dB larger than the minimum receiver sensitivity Adjacent channel rejection –Conforming OFDMA signal –At least 11 dB power above than desired signal when 16-QAM-3/4 –At least 4 dB power above than desired signal when 64-QAM-2/3 Non-adjacent rejection –Any channel other than adjacent channel or co-channel –At least 30 dB power above than desired signal when 16-QAM-3/4 –At least 23 dB power above than desired signal when 64-QAM-2/3 BER < 10 -6

Proprietary of NTHU Communication SOC Lab, 2006 AAS Support Indicated by IEs in the DL and UL broadcast maps AAS zone –A contiguous block of OFDMA symbols –Defined preamble structure –May contain an optional Diversity-Map scan zone (D-Msz) Used only with FFT size larger than or equal to 512 Used to transmit AAS-DLFP AAS frame structure –Consists of subchannels –PUSC, FUSC, oFUSC permutation Two highest numbered subchannels of DL frame may contain D-Msz –AMC permutation The first and last numbered subchannels of AAS DL zone may contain D- Msz A 2 bin by 3 symbol tile structure is used

Proprietary of NTHU Communication SOC Lab, 2006 AAS Support –In a given AMC subchannel, the beam pattern for all pilot and data subcarriers is the same –In a PUSC permutation, the SS assume the major group is beamformed Channel may very slowly over the zone

Proprietary of NTHU Communication SOC Lab, 2006 Optional Diversity-Map scan AAS-DLFP (Down Link Frame Prefix) –A robust transmission of the required BS parameters Enable SS initial ranging SS paging and access allocation –QPSK-1/2, 2 repetitions –Start with an AAS DL preamble –Specified the permutation of AAS UL Zone –May, but need not carry the same information –Supports the ability to transmit a compressed DL-MAP IE –Not randomized

Proprietary of NTHU Communication SOC Lab, 2006 AAS Network Entry AAS-SS synchronizes frame timing and frequency by DL preamble If decoding of broadcast map fails, search for AAS-DLFP over several permutations The SS may receive DCD and UCD pointed from AAS-DLFP Perform initial ranging using information from DCD and UCD, where the ranging interval is pointed by AAS-DLFP Wait the ranging response Normal operation

Proprietary of NTHU Communication SOC Lab, 2006 AAS Preambles AAS preambles –Training information in both UL and DL AAS zone –Preceding all data allocation and AAS DLFP in AAS zone –Length is specified in the AAS_DL_IE and AAS-DLFP –Either time or frequency shifted AAS DL preamble –Preamble length of AAS-DLFP is 1 symbol duration –In PUSC permutation, preamble length is 0 or 2 symbols AAS UL preamble –The first Uplink_preamble_config symbols are reserved for UL AAS preambles –Inserted at the start of an UL data allocation by 3 symbol duration

Proprietary of NTHU Communication SOC Lab, 2006 AAS DL Preamble Formed by concatenating the original preamble sequence The length of basic preamble is N used bits BPSK modulation DC carrier shall not be modulated A subset of the basic preamble is used for burst

Proprietary of NTHU Communication SOC Lab, 2006 AAS UL Preamble The basic preamble is the same as AAS DL preamble A subset of the basic preamble is used for burst Preamble power level when lower bound < C/N < upper bound otherwise

Proprietary of NTHU Communication SOC Lab, 2006 Preamble Shift Time shift Frequency shift K = [AAS_beam_index (mod 14)]*N fft /14 for PUSC K = [AAS_beam_index (mod 14)]*Nfft/9 for AMC

Proprietary of NTHU Communication SOC Lab, 2006 STC Using 2 Antennas STC may be used on the downlink to provide higher order diversity –2 transmit antennas on BS –1 reception antenna on SS –Similarly maximal ratio combining (MRC) Transmit two different OFDMA symbol in the same time

Proprietary of NTHU Communication SOC Lab, 2006 STC Encoding Antenna: A 0,A 1 Channel vector: h 0, h 1 Transmission complex symbol: s 1, s 2 –First transmission : A 0 for s 1, A 1 for s 2 –Second transmission : A 0 for –s 2 *, A 1 for s 1 * The estimates benefit from second order diversity as in 1Tx-2Rx MRC scheme May be used both in PUSC and FUSC configurations

Proprietary of NTHU Communication SOC Lab, 2006 STC2 in PUSC The data allocation to cluster is slightly modified –STC encoding is done on each pair of symbols 2n, 2n+1 (n = 0,1,..)

Proprietary of NTHU Communication SOC Lab, 2006 STC4 in PUSC

Proprietary of NTHU Communication SOC Lab, 2006 STC2 in FUSC Pilot for even symbol –A 0 : Variable set #0 and Constant set #0 –A 1 : Variable set #1 and Constant set #1 Pilot for odd symbol –A 0 : Variable set #1 and Constant set #0 –A 1 : Variable set #0 and Constant set #1

Proprietary of NTHU Communication SOC Lab, 2006 STC4 in FUSC

Proprietary of NTHU Communication SOC Lab, 2006 Frequency Hopping Diversity Coding The downlink preamble shall be transmitted for the duration of one OFDMA symbol from Antenna 0 Transmission complex symbol: s 1, s 2 Antenna: A 0,A 1 –A 0 : transmits mapped carriers for subchannel X(s 1 ) onto subchannel X, and mapped carriers for subchannel X+1(s 2 ) onto subchannel X+1 –A1: transmits mapped carriers for subchannel X(-s 2 * ) onto subchannel X, and mapped carriers for subchannel X+1(s 1 * ) onto subchannel X+1

Proprietary of NTHU Communication SOC Lab, 2006 STC Decoding STC using 2 antennas FHDC

Proprietary of NTHU Communication SOC Lab, 2006 Uplink Using STC (1/2) A user-supporting transmission using STC configuration in the uplink –2-transmit diversity data (STTD mode) –2-transmit spatial multiplexing data (SM mode) –Mandatory tile structure shall be used with modification

Proprietary of NTHU Communication SOC Lab, 2006 Uplink Using STC (2/2) STTD mode –The tiles shall be allocated to subchannels and the data subcarriers enumerated – data subcarriers shall be encoded in pairs SM mode (subcarrier) –Two single transmit antenna SS’s can perform collaborative spatial multiplexing onto the same subcarrier –A single user having two antennas may do UL spatial multiplexing Horizontal coding - 2 bursts concurrently Vertical coding - 1 burst (2 slots) concurrently SM mode (subchannel) –one SS should use the uplink tile with pattern-A while the other uses B –Two dual antenna SS one SS should use the uplink tile with the pilot pattern A, B one SS should use the uplink tile with the pilot pattern C, D

Proprietary of NTHU Communication SOC Lab, 2006 STC2 Enhancement Using 4 antennas –2 are used in order to transmit each symbol –2 transmit the same signal with a complex multiplication –Antenna weights may be changed by BS with SS information using feedback channel (CQI channel) –No change of the estimation process