Multi-block OFDM for TVWS Operation May 2010 doc.: IEEE 802.11-10/0608r0 May 2010 doc.: IEEE 802.11-10/0608r0 Multi-block OFDM for TVWS Operation Authors: Submission Slide 1 Meng Wah Chia (I2R)

Discontinuous TVWS Channel May 2010 doc.: IEEE 802.11-10/0608r0 Discontinuous TVWS Channel CH 20 CH 22 CH 24 CH 26 CH 21 CH 23 CH 25 CH 28 CH 30 CH 27 CH 29 CH 31 The spectrum opportunity of TVWS consists of fragments of different number of available TV channels. These TV channels may or may not be contiguous, and may even be spaced far apart (e.g. a secondary user to access CH 21, 24, 28) The 802.11af should support the usage of multiple available channels in TVWS. Submission Slide 2 Meng Wah Chia (I2R)

May 2010 doc.: IEEE 802.11-10/0608r0 May 2010 doc.: IEEE 802.11-10/0608r0 NC-OFDM CH 20 CH 22 CH 24 CH 26 CH 21 CH 23 CH 25 CH 28 CH 30 CH 27 CH 29 CH 31 PU PU PU Non-Contiguous OFDM (NC-OFDM) uses an OFDM system with a large bandwidth to span over multiple TVWS channel (e.g. from CH 20 to 29). Information about TVWS availability obtained through spectrum sensing or database access. Nulls are transmitted on frequency bands occupied by the primary users (PU). (e.g. CH 21). Submission Slide 3 Meng Wah Chia (I2R)

May 2010 doc.: IEEE 802.11-10/0608r0 Multi-Block OFDM Multi-Block OFDM uses K-OFDM systems to transmit over multiple TVWS channels. Spectrum sensing measurements obtain information about TVWS availability. The center frequency of each OFDM block is adjusted such that it transmits in the dedicated TVWS channel. …. + Submission Slide 4 Meng Wah Chia (I2R)

Multi-Block OFDM Receiver May 2010 doc.: IEEE 802.11-10/0608r0 Multi-Block OFDM Receiver …. The received signal is down-converted into K parallel streams. Submission Slide 5 Meng Wah Chia (I2R)

NC-OFDM vs Multi-block OFDM May 2010 doc.: IEEE 802.11-10/0608r0 NC-OFDM vs Multi-block OFDM CH 20 CH 22 CH 24 CH 26 CH 21 CH 23 CH 25 CH 28 CH 30 CH 27 CH 29 CH 31 1 OFDM NC-OFDM is not an effective solution when: There are many channels occupied by the PU (e.g. when CH 21 to 27 are used by the PU): Nulls on subcarriers. The available channels are spaced far apart (e.g. only CH 21 and 29 are to be used) Multi-block OFDM Dynamic spectrum access of non-adjacent channels Simultaneous access over multiple frequency Submission Slide 6 Meng Wah Chia (I2R)

Case 1: Modulation Dependent Parameters May 2010 doc.: IEEE 802.11-10/0608r0 Case 1: Modulation Dependent Parameters Preamble Signal Data 5 MHz K=1 OFDM 64 μs 16 μs 16 μs OFDM OFDM 10 MHz K=2 32 μs 8 μs OFDM OFDM OFDM OFDM 20 MHz K=4 OFDM OFDM OFDM OFDM time 16 μs 4 μs 4 μs K: Number of active OFDM units, and depends on the number of available TVWS channels Submission Slide 7 Meng Wah Chia (I2R)

Carrier Aggregation May 2010 doc.: IEEE 802.11-10/0608r0 : OFDM 1 OFDM 2 : OFDM K Carrier aggregation unit assigns the data into K OFDM blocks. Each OFDM unit has 64 subcarriers. Let the bandwidth of the kth OFDM block be Bk. Number of OFDM symbols transmitted by the kth block Number of OFDM block within TLong Number of repetition of the kth OFDM block Longest OFDM signal duration Submission Slide 8 Meng Wah Chia (I2R)

Case 2: Modulation Dependent Parameters May 2010 doc.: IEEE 802.11-10/0608r0 Case 2: Modulation Dependent Parameters Preamble Signal Data 5 MHz K=1 OFDM 64 μs 16 μs 16 μs OFDM OFDM …. OFDM 10 MHz K=2 OFDM OFDM OFDM …. OFDM 32 μs 8 μs OFDM OFDM OFDM …. OFDM 20 MHz K=4 OFDM time 16 μs 4 μs 4 μs Submission Slide 9 Meng Wah Chia (I2R)

Carrier Aggregation May 2010 doc.: IEEE 802.11-10/0608r0 : OFDM 1 OFDM 2 : OFDM K Carrier aggregation unit assigns the data into K OFDM blocks. Each OFDM unit has 64 subcarriers. Let the bandwidth of the kth OFDM block be Bk. Number of OFDM symbols transmited by the kth block Number of OFDM block within TLong Number of data OFDM signal for the kth OFDM block Longest OFDM signal duration Submission Slide 10 Meng Wah Chia (I2R)

May 2010 doc.: IEEE 802.11-10/0608r0 May 2010 doc.: IEEE 802.11-10/0608r0 Carrier Sensing Due to the requirement to sense over multiple bands, we have 2 carrier sensing carrier sensing methods: Full-sensing of bands (1,…, K). Set carrier sensing outcome = OR (carrier sensing outcome of band 1, ..., carrier sensing outcome of band K). Partial-sensing of bands (1,…, n, where n K). Set carrier sensing outcome = OR (carrier sensing outcome of band 1, ..., carrier sensing outcome of band n). Virtual Carrier Sensing: Full sensing of bands (Sense all bands) Partial sensing of bands (Sense one of the bands) Submission Slide 11 Meng Wah Chia (I2R)

Suppose we transmits over K-TVWS channels. May 2010 doc.: IEEE 802.11-10/0608r0 Suppose we transmits over K-TVWS channels. Multi-Block OFDM NC-OFDM FFT Points (per OFDM Unit) NSC NSC x K Complexity KNSC log NSC KNSC log (NSC K) Receiver Complexity K down-conversion units 1 down-conversion unit Support for coexistence Uses multiple OFDM centered at multiple TVWS frequencies Transmit nulls on non-TVWS channels General Concerns Inefficient in contiguous band operation Inefficient in non-contiguous band operation Submission Slide 12 Meng Wah Chia (I2R)

May 2010 doc.: IEEE 802.11-10/0608r0 MAC Amendments : New Information Element (IE) in Beacon Period (BP) contains information about Number of channels Channel center frequencies … TVWS Availability … Time This interval is large compared to the beacon interval BP Quiet Period BP Beacon Interval Submission Slide 13 Meng Wah Chia (I2R)

May 2010 doc.: IEEE 802.11-10/0608r0 Conclusion Proposed multi-block OFDM as an efficient TVWS PHY design, suitable when: PU occupies most of the available bands. Available TVWS channels are spaced far apart. Proposed carrier aggregation and carrier sensing rules required for Multi-block OFDM. Proposed MAC amendments for multi-block OFDM. Information element in Beacon Period Submission Slide 14 Meng Wah Chia (I2R)

Thank You. May 2010 doc.: IEEE 802.11-10/0608r0 Submission Slide 15 Meng Wah Chia (I2R)