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SDM 202
Comparison of SDM with IEEE 802.16d OFDM RF Efficiencies and Digital Capacities
The following table compares SDM relative RF efficiences and physical layer time-based over head to that of IEEE 802.16d-REVd/D3-2004, Section 8.3 OFDM. Many of these comparisions are also true for Section 8.4 OFDMA, however the frequency based overheads of multiple segments and therefore multiple pilot sub-channels has not been taken into consideration.
Latency calculations only take into consider ReedSolomon (RS) coding for OFDM, and RS and SDM Coding (BFEC) for SDM. Latency attributed to other coding and/or interleaving has not been enumerated.
Cooked capacity is that which is delivered post FEC and codings to the PHY-TC Layer and/or MAC Layer.
The comparisons column shows the percent gains in RF efficiency of SDM in both the frequency and time domains.
There are further gains of SDM in performance areas that need to be enumerated in the future.
Frequency
and Time Overhead Efficiencies of IEEE 802.16d-REVd/D3-2004 |
Frequency
and Time Efficiencies of SDM |
SDM/OFDM | ||||||||
| Overview of OFDM Section 8.3 | Min% | Max% | ||||||||
| BW (Hz) | 1,750,000 | BW (Hz) | 1,750,000 | |||||||
| Nused subchannels | 200 | Nused Sub-bands | 68 | |||||||
| n Samplling factor (8/7's or 1.14) | 1.14 | |||||||||
| Nfft | 256 | Total Sub-bands | 128 | |||||||
| Fs (floor(n*BW)/0.008)*0.008 | 2,000,000 | |||||||||
| DeltaF subcarrier spacing (Hz) | 7,812.5 | Sub-band Width (Hz) | 25,000.0 | |||||||
| Pilot subcarriers | 8 | Pilot subcarriers | not applicable | |||||||
| DC subcarrier | 1 | DC subcarriers | not applicable | |||||||
| Pilot/DC subcarrier overhead | 4.5% | |||||||||
| UsedDataF (Hz, for data) | 1,492,188 | UsedDataF (Hz) | 1,700,000 | |||||||
| UsedDataF to BW ratio | 85% | UsedDataF to BW ratio | 97% | 14% | ||||||
| Tb (seconds, Useful symbol time) | 0.000128 | Tb | not applicable | |||||||
| G (ratio of CP to Useful time) | 1/32 | 1/16 | 1/8 | 1/4 | G | not applicable | ||||
| Tg (seconds, CP time) | 0.000004 | 0.000008 | 0.000016 | 0.000032 | Tg | not applicable | ||||
| Ts (OFDM symbol time secs/sym) | 0.000132 | 0.000136 | 0.000144 | 0.000160 | ||||||
| Ratio (Ts-Tg)/Ts | 0.97 | 0.94 | 0.89 | 0.80 | SDM Sync Overhead (in time) | 0.78% | ||||
| SymRate (symbols/second) | 7,576 | 7,353 | 6,944 | 6,250 | SDM Symbol Rate (symbols/second) | 50000 | ||||
| Sampling Time (seconds, Tb/Nfft) | 0.0000005 | SDM Symbol Time (seconds/symbol) | 0.0000200 | |||||||
| Mod+Demod Latency (approx) | 0.000528 | 0.000544 | 0.000576 | 0.000640 | Mod+Demod Latency (approx) | 0.000400 | 24% | 38% | ||
| RawRates (bps) | RawRates (bps) | |||||||||
| QPSK | 2,893,939 | 2,808,824 | 2,652,778 | 2,387,500 | 1SDM (2bps/Hz) | 3,400,000 | 17% | 35% | ||
| 16QAM | 5,787,879 | 5,617,647 | 5,305,556 | 4,775,000 | 2SDM (4bps/Hz) | 6,800,000 | 17% | 35% | ||
| 64QAM (optional) | 8,681,818 | 8,426,471 | 7,958,333 | 7,162,500 | 3SDM (6bps/Hz) | 10,200,000 | 17% | 35% | ||
| RawRateEff (rawbits/second/BW) | RawRateEff (rawbits/second/BW) | |||||||||
| QPSK | 1.7 | 1.6 | 1.5 | 1.4 | 1SDM | 1.9 | ||||
| 16QAM | 3.3 | 3.2 | 3.0 | 2.7 | 2SDM | 3.9 | ||||
| 64QAM (optional) | 5.0 | 4.8 | 4.5 | 4.1 | 3SDM | 5.8 | ||||
| BPS (Post RS FEC) | BPS (Post RS FEC) | |||||||||
| QPSK-1/2 | 1,446,970 | 1,404,412 | 1,326,389 | 1,193,750 | ||||||
| QPSK-3/4 | 2,170,455 | 2,106,618 | 1,989,583 | 1,790,625 | 1SDM (BFEC+RS) | 2,541,689 | 17% | 35% | ||
| 16QAM-1/2 | 2,893,939 | 2,808,824 | 2,652,778 | 2,387,500 | ||||||
| 16QAM-3/4 | 4,340,909 | 4,213,235 | 3,979,167 | 3,581,250 | 2SDM (BFEC+RS) | 5,628,025 | 30% | 47% | ||
| 64QAM-2/3 (optional) | 5,787,879 | 5,617,647 | 5,305,556 | 4,775,000 | ||||||
| 64QAM-3/4 (optional) | 6,511,364 | 6,319,853 | 5,968,750 | 5,371,875 | 3SDM (BFEC+RS) | 8,714,362 | 34% | 51% | ||
| Cooked Efficiency (cookedbits/sec/Hz) | Cooked Efficiency (cookedbits/sec/Hz) | |||||||||
| QPSK-1/2 | 0.8 | 0.8 | 0.8 | 0.7 | ||||||
| QPSK-3/4 | 1.2 | 1.2 | 1.1 | 1.0 | 1SDM | 1.5 | ||||
| 16QAM-1/2 | 1.7 | 1.6 | 1.5 | 1.4 | ||||||
| 16QAM-3/4 | 2.5 | 2.4 | 2.3 | 2.0 | 2SDM | 3.2 | ||||
| 64QAM-2/3 (optional) | 3.3 | 3.2 | 3.0 | 2.7 | ||||||
| 64QAM-3/4 (optional) | 3.7 | 3.6 | 3.4 | 3.1 | 3SDM | 5.0 | ||||
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