Performance of PBCC and CCK

1. Performance of PBCCand CCK Matthew Shoemake, Stan Ling & Chris Heegard Alantro

2. PBCC • 64 state binary convolutional encoder • Encoder requires 6 bits of memory • Modulated onto QPSK, just like CCK Alantro

3. CCK • CCK is an 8 bit in, 16 bit out block code • CCK is rate 1/2, just like PBCC • CCK is described by a generator over Z4 G = [ 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1] (see doc 98-303) Alantro

4. Complexity • CCK requires 26 adds per info bit • PBCC requires 132 adds per info bit • CCK requires 16 compares per info bit • PBCC requires 64 compares per info bit Alantro

5. Bit Error Rate 0 10 -1 10 -2 10 BER -3 10 -4 10 -5 10 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 Es/No Bit Error Rate Alantro

6. Block Error Rate 0 10 -1 10 BER -2 10 -3 10 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 Es/No Block Error Rate Alantro

7. Multipath 64 byte packets Alantro

8. Multipath, 1000 byte packets Alantro

9. What 3dB is worth • Cell Size IncreaseAn additional 3 dB coding gain equates roughly to a 30% increase in transmission distance in an open-air environment. For a given service area, the number of cells is roughly proportional to the service area divided by the transmission distance squared (area/p*distance ^ 2). With a 3dB gain, the area covered by a cell is 70% larger which means that the number of cells required is reduced to approximately 60% that of a standard FEC system for the identical service area. • Reduced Power at the ClientThe user/network operator can configure the system to utilize the optional FEC for the access point to client transmission (AP -> C), the client to access point transmission (C -> AP), or both. One possible scenario is to use the optional, high-performance FEC for C -> AP transmission and the standard FEC for AP -> C transmission. Only the low-cost/low-complexity encoder of the optional FEC is implemented at the client, while the increased complexity and power of the high-performance decoder are consumed at the access point, where the power and complexity are not as critical. On the C -> AP transmission, the client may transmit at a lower power than the AP -> C transmission, yet still retain equivalent performance. The result is lower power consumption at the client, increasing the operating time at the point where it is needed. Alantro

10. What 3dB is worth (cont.) • Greater Building PenetrationAn additional 3 dB coding gain allows the system to achieve transmission “through one more wall”. This again yields an increased cell size and more flexible cell/network planning.System Robustness in the ISM BandsNew services are beginning to crowd the ISM bands utilized by the 802.11 2.4 GHz wireless LAN standard. An additional 3 dB coding gain provides system robustness and operating margin against existing and emerging services within the 2.4 GHz ISM bands. • Higher Network ThroughputAn additional 3 dB coding gain improves network throughput. First, an additional 3 dB coding gain improves the performance of marginal clients. Clients operating at a 30 ~ 40% packet error rate with the standard FEC can now operate at 10% PER with the optional high-performance FEC. Second, clients operating at 10% PER with the standard FEC can now operate at significantly lower PERs with the optional high-performance FEC. In either case, the overall throughput of the network will increase significantly. Alantro