IEEE P802.22 Wireless RANs Date: 2006-10-09 October 2006 doc.: IEEE 802.22-06/015r2 October 2006 ADAPTIVE TDD for 802.22 WRANs IEEE P802.22 Wireless RANs Date: 2006-10-09 Authors: Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org. > Ying-Chang Liang, I2R Ying-Chang Liang, I2R

October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Why Adaptive TDD? Adaptive TDD overcomes the problem of long TDD turn-around time in WRANs. Adaptive TDD significantly increases the system capacity of WRANs. Adaptive TDD can be implemented in a simple, flexible, efficient, and evolvable manner. All the WG need to do is to add one extra subsection (less than 1 page) to the current Draft. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

FRD Compliance Table – Req. 31: October 2006 doc.: IEEE 802.22-06/015r2 October 2006 FRD Compliance Table – Req. 31: 31 (3) If TDD is proposed, the proposal MUST include diagrams illustrating the proposed framing/timing and analysis of the impact of TDD turn-around time on system capacity, latency, and other factors affecting performance and overall system complexity. M Y (analysis has been made in a separate document*) 6.13.1-6.13.4 * 22-06-0104-01-0000_ADAPTIVE_TDD.doc Section 6.13.1 of Draft 0.1: “TDD is the mandatory duplexing mode.” Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Impact of TDD Turn-around Time October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Impact of TDD Turn-around Time Assume 6Mhz channel, 2K FFT, ¼ CP, 50us max delay spread, 10ms frame. Nearby CPEs need to be idle for: More than 1 OFDMA symbol for cell radius of 30km. More than 2 OFDMA symbols for cell radius of 100km. => For WRANs with large cell radius, TDD turn-around time leads to long DS-US gap and significantly reduces system capacity. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Concepts of Adaptive TDD October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Concepts of Adaptive TDD TDD turn-around time BS DS Subframe US1-1 US 1,2 CPE1 DS Subframe US1-1 US1-2 TPD1 TDS1 TSSRTG CPE2 DS Subframe US2-1 TPD2 TDS2 TSSRTG TPD2 Allow nearby CPEs to start US transmission earlier than faraway CPEs. Keep OFDMA symbol boundaries synchronized at BS. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Gain in UL Throughput October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Gain in UL Throughput Cell radius = 30km, nearby CPEs within 5km from BS can transmit 1 OFDMA symbol earlier. Nearby CPEs use 64QAM, ¾ code rate; faraway CPEs use QPSK, ½ code rate. DS and US traffics are symmetric. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Upstream Subframe Structure October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Upstream Subframe Structure OFDMA Symbols Divide US subframe into “Early zone” and “Normal zone”. The size of each zone can be made flexible by adjusting the “Allocation Start Time”. Slot-allocation rules are the same for the two zones. Logical Subchannels Early Start Time Allocation Start Time Ying-Chang Liang, I2R Ying-Chang Liang, I2R

US MAP IE for AdaptiveTDD Bursts October 2006 doc.: IEEE 802.22-06/015r2 US MAP IE for AdaptiveTDD Bursts October 2006 Syntax Size Notes US-MAP_IE() { CID 16 bits UIUC 4 bits = 15 AdpativeTDD_IE() 24 bits Padding Nibble = 0x04 } Using an US Extended UIUC, called AdaptiveTDD IE, to specify Adaptive TDD bursts. To specify each AdaptiveTDD burst we need 48 bits, the same as that for normal uplink TDD bursts. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

AdaptiveTDD_IE (Extended UIUC) October 2006 doc.: IEEE 802.22-06/015r2 October 2006 AdaptiveTDD_IE (Extended UIUC) Syntax Size Notes AdaptiveTDD_IE() { Extended UIUC 4 bits 0x0F Length 0x02 (in bytes) Burst_Profile 3 bits From 6 to 12 Early Start Time = n n = 0 => not employing Adaptive TDD n > 0 => Adaptive TDD is employed, starts n 0FDMA symbols earlier than what specified by the Allocation Start Time in the US-MAP. Preamble Present 1 bit Determines whether CPE shall send preamble before any data transmission 0 = Preamble shall not be used (default) 1 = Preamble shall be used Duration} 8 bits In number of MAC slots Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Proposed Text Addition to Draft 0.1 October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Proposed Text Addition to Draft 0.1 We propose to add a new section: “Section 6.8.4.1.2.3 AdaptiveTDD IE” to the current v.0.1 document. In particular, the new Section will be as follows. 6.8.4.1.2.3 AdaptiveTDD IE Each AdaptiveTDD IE is 3 byte long and is specified as in Table 1. The important fields of this extended IE are: Extended UIUC: this 4 bit field is set to 0x0F to indicate an AdaptiveTDD IE. Length: length of data field = 2 bytes. UIUC: this 4 bit field specifies the burst profile of the corresponding AdaptiveTDD IE. Early Start Time: this is a 2-bit field that specifies how early this AdaptiveTDD IE should start, with respect to the global Allocation Start Time specified in the US MAP. Duration: The duration of the AdaptiveTDD IE in OFDMA slots. Syntax Size Notes AdaptiveTDD_IE() {   Extended UIUC 4 bits 0x0F Length 0x02 (in bytes) Burst_Profile 3 bits From 6 to 12 Early Start Time = n n = 0 => not employing Adaptive TDD n > 0 => Adaptive TDD is employed, starts n 0FDMA symbols earlier than what specified in the US-MAP. Preamble Present 1 bit Determines whether CPE shall send preamble before any data transmission 0 = Preamble shall not be used (default) 1 = Preamble shall be used Duration} 8 bits In number of MAC slots Table 1: Format of an AdaptiveTDD IE Each AdaptiveTDD IE allocation shall be restricted within its early US portion, i.e., between its Early Start Time and the Allocation Start Time. Each AdaptiveTDD IE allocation shall start at the unused MAC slot that has the lowest subchannel index followed by the lowest symbol index (i.e., subchannel index has higher priority than symbol index). Each AdaptiveTDD IE allocation shall advance in the time domain and shall not overlap with the previous AdaptiveTDD allocations. If the end of the Early US Portion has been reach, the allocation shall continue at the next subchannel at the first symbol, specified by its Early Start Time. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

Other Mandatory Requirements October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Other Mandatory Requirements [26] In the upstream direction, 802.22 protocols MUST provide the means to efficiently multiplex traffic from multiple CPEs and allocate transmission channel capacity. [47] The PHY and MAC protocols SHALL flexibly accommodate communication between a base station and CPEs at distances of up to 100 km where feasible. [53] Ranging SHALL be done to synchronize CPEs with a common time reference relative to base station timing  in order to maximize the transmission medium capacity by minimizing guard time requirements. [87] The PHY and MAC protocols SHALL provide the ability to adaptively deliver different bit rates/capacities to individual subscribers. Ying-Chang Liang, I2R Ying-Chang Liang, I2R

October 2006 doc.: IEEE 802.22-06/015r2 October 2006 Conclusions Adaptive TDD mitigates the problem of long turn-around time and significantly increases system capacity. Adaptive TDD can be implemented in a flexible, efficient, and evolvable manner. All the WG need to do is to add one extra subsection (less than 1 page) to the current Draft. Ying-Chang Liang, I2R Ying-Chang Liang, I2R