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Doc.: IEEE 802.22-05/0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 1 A Cognitive PHY/MAC Proposal for IEEE 802.22 WRAN Systems IEEE P802.22.

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Presentation on theme: "Doc.: IEEE 802.22-05/0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 1 A Cognitive PHY/MAC Proposal for IEEE 802.22 WRAN Systems IEEE P802.22."— Presentation transcript:

1 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 1 A Cognitive PHY/MAC Proposal for IEEE WRAN Systems IEEE P Wireless RANs Date: Authors: Notice: This document has been prepared to assist IEEE 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at

2 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 2 PHY Abstract Digital modulation systems presently make use of two basic modulation technologies: single carrier and multi-carrier. Their features are well-known since they have been deployed for several years around the world for broadcasting applications. Wireless access applications differ from broadcasting since they require :  flexibility on the downstream link : variable number of user, variable throughput per user, variable level of protection, etc;  multiple access on the upstream link. Single carrier modulation can tackle these objectives through time multiplexing techniques. Multi-carrier modulation is however more flexible since it enables to control the signal in both time and frequency domains. This gives the opportunity to define two dimensional (time and frequency) slots and to map the services to be transmitted in both directions onto a subset of these slots. Two types of multi-carrier modulation has been retained in IEEE (WiMAX) standard: OFDM in the fixed MAN version and OFDMA in the mobile version. In the continuity of IEEE , it is proposed here to consider OFDMA modulation for downstream and upstream links with two technological improvements: Spreading; OQAM waveforming. To meet the tight link budget requirements of WRAN, duo binary turbo code is proposed for service ranges up to 100 Km

3 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 3 MAC Abstract We propose the Cognitive MAC (CMAC) layer to be used as the basis for the future IEEE WRAN standard operating in the TV bands. The proposed CMAC is in some respects inspired by the IEEE standard, but it provides major extensions, improvements and also simplifications in order to meet the functional requirements. CMAC is based on a superframe architecture which is general enough to allow multiple wireless systems to coexist in addition to support the flexibility to group multiple vacant TV channels and hence achieve greater capacity. To coexist with incumbent services, CMAC is able to efficiently manage distributed incumbent measurement, control, and recovery procedures, while also providing the necessary spectrum management features. To coexist amongst systems, CMAC is the first of its kind to implement a novel coexistence beacon protocol (CBP) that allows BSs with overlapping coverage areas to coordinate and efficiently share the radio spectrum, hence minimizing interference. The efficiency of CBP is further improved by a new scheme that dynamically synchronizes overlapping BSs. Additional characteristics of CMAC include the support of various traffic types with different QoS requirements, flexible bandwidth management, and a combination of access mechanisms.

4 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 4 Presentation Outline Introduction –A Glimpse of IEEE The Cognitive PHY Proposal The Cognitive MAC Proposal Conclusions

5 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 5 Presentation Outline Introduction –A Glimpse of IEEE The Cognitive PHY Proposal The Cognitive MAC Proposal Conclusions

6 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 6

7 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 7 The IEEE From 18 Mbps to 24 Mbps Propagation delays in excess of 300 µs Operates in TV bands –54 to 862 MHz –6 MHz, 7 MHz and 8 MHz channel bandwidth

8 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 8 Deployment Scenario Master/Slave relationship Entities –Base Station (BS) –Consumer Premise Equipment (CPE) 4W CPE transmit power

9 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 9 Presentation Outline Introduction –A Glimpse of IEEE The Cognitive PHY Proposal The Cognitive MAC Proposal Conclusions

10 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 10 PHY Presentation Outline Background Top-level description of modulation/coding Channel bonding Modulation Parameters Spreading OFDMA Sensing techniques OQAM/OFDMA Duo-binary CTC

11 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide requirements consideration Regional Area Network (up to 30Km) –Operate in vacant TV bands –Detect vacant TV bands Large delay spread and roundtrip time Data rate: from 1.5 Mbps DS and ~300 Kbps US Should not cause harmful interference to other devices –-70dB OOB emission –detect and avoid Flexibility –Bandwidth, bit rate, TX power, access mechanism, etc Spectral efficiency 4 watt transmission power

12 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 12 PHY Overview OFDMA both in uplink and downlink QPSK, 16-QAM, and 64-QAM, spreaded-QPSK More than 32 sub channels Contiguous channel bonding upto 3 TV channels ( and beyond in a stack manner) Data rate range from 5Mbps to 60Mbps Option of OQAM/OFDMA and turbo code

13 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 13 Why OFDMA ? Single carrier and multi-carrier have been used for broadcasting, wireless access, etc –Their behavior is well understood (capacity, filtering requirements, PAPR, equalization, flexibility, efficiency) Wireless access differ from broadcasting and most other system –flexibility in downstream and upstream link –variable # of users, variable throughput, –large round-trip signal delay –multiple access Multi-carrier system more suitable to meet these objectives –It enables to control the signal in time and frequency –Results in a two dimensional grid to assign resources to a user  OFDMA –Resources can be allocated on a per user basis OFDM used in standards such as –WiMedia UWB, WiMAX (Fixed MAN), DAB, DMB, DVB-T, DVB-H, ISDB-T OFDMA used in WiMax, DVB-RCT

14 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 14 OFDMA Based on OFDMA (sub-channels per user) –US/DS –Reduces overhead for short messages –Flexibility in choosing modulation/coding for CPE –Reduced PAPR for CPEs

15 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 15 Coding

16 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 16 Modulation

17 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 17 Channel Bonding More data rate Multi-path Diversity –Small BW signal can have deep fade or flat fade –Wider-bandwidth signal provides more frequency/multipath diversity Interference –Wider-band reduces the amount of interference

18 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 18 Channel Bonding/capacity Aggregate TV channels to get more capacity –Shannon: C = B.log2(1+S/N) –Capacity proportional to BW, but logarithmic with SNR or signal power If S/N is fixed, then capacity increases linearly with bandwidth If signal power is fixed, but bandwidth is increased –C = B.log2(1+S/(BNo)) –Capacity still increases as bandwidth is increased

19 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 19 Capacity of aggregated channels as a given signal power is spread over more channels

20 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 20 Channel bonding 6, 12, 18 MHz channels Depends on availability Several receiver techniques to deal with flexible BW –Selectable analog filters –Up sampling digital filters

21 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 21 Channel bonding structure 6K FFT over 3 TV channels –2K per TV channel –Null out the outer carriers for 1 or 2 TV channels Fixed inter-carrier spacing –Several implementation possibilities 12 MHz 6 MHz 18 MHz

22 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 22 Frame structure: Superframe

23 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 23 Spectrum of the signal (before further filtering) Produced using a 6K FFT for a single TV channel

24 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide proposed relative RF emission

25 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 25 Inter-carrier spacing and FFT/IFFT period values for different bandwidth options Table 2: Inter-carrier spacing and FFT/IFFT period values for different bandwidth options 6 MHz based channels (6, 12 and 18 MHz) 7 MHz based channels (7, 14 and 21 MHz) 8 MHz based channels (8, 16 and 24 MHz) Inter-carrier spacing,  F (Hz) FFT/IFFT period, T FFT (  s)

26 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 26 OFDMA parameters

27 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 27 Modulation/coding modes and corresponding rates

28 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 28 Preamble Superframe preamble –Over 1512 sub-carriers (every fourth or second non-zero), –5 MHz BW –Simply duplicate for additional TV channels –1 MHz gap between adjacent channels to relax filtering –2 symbol duration (1 more for data) Frame preamble: 1-3 TV channels –1728*N sub-carriers –Short preamble is optional (short) (long)

29 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 29 Spreaded QPSK/OFDMA Spread data over some sub-carriers (Hadamard) Increases capturing of multipath diversity Increases resiliency to interferers Simple receiver structure (MMSE)

30 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 30 Simulation results for QPSK, rate 3/4 S-OFDMA gives 2-4dB gain! Channels: ATSC Brazil D Profile A All with Doppler

31 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 31 Preliminary Link Budget(LOS)

32 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 32 Other Features Ranging Transmitter Power Control (TPC) Consideration of multiple antenna

33 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 33 Channel Measurement Received signal strength –Quality measurement of its own signal (TPC, modulation/coding) –Fast channel ‘busy’ detection Signal feature detection –Detection of the type of the signal ATSC, DVB-T, Part 74,.22, etc –Should be robust to receiver imperfections

34 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 34 Received Signal Strength Several implementation techniques –FFT, IOTA/FFT, simple low-pass filter etc –Possibility to measure a part of the spectrum Various degrees of performance Integration time and threshold is very important BS sets essential parameters (constant) Either the BS makes the detection decision based on the collective measurement results or CPE’s can make the decision –distributed measurement

35 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 35 Simulated performances of OFDM and OQAM: detecting ATSC pilot 5ms integration time

36 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 36 DTV signal feature detection Should not be sensitive to frequency selective fading, and receiver impairments (e.g., frequency error) Use field sync correlation detection for ATSC, similar correlation for other standards –Compare correlation peak to the mean of the standard deviation of the correlation –Characterized the theoretical performance –Experimental tests

37 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 37 MULTIPATH SIMULATOR ATTENUATOR RECEIVER 8VSB_SOURCE Experimental setup for DTV detection

38 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 38 Based on DTV Laboratory Test Plan (Group C.1) “Static Echoes at various delays”.

39 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 39 Based on DTV Laboratory Test Plan (Group D.1) “Static multipath with AWGN”.

40 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 40 Based on Doc.: IEEE /0055r7. Profile A.

41 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 41 Based on Doc.: IEEE /0055r7. Profile B.

42 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 42 Part 74 detection Part 74 devices occupy a small portion of the spectrum Thus, use spectral estimation and statistics of the estimated signal –Spectral estimation using FFTs (windowing techniques can also be employed to better localize the spectrum) Perform FFT Average each freq bin Average across freq bin –Compute mean and “variance” FFT avg W.F. V>k*avg

43 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 43 Part 74 detection (cont.) Detection Theoretical performance

44 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 44 Narrow-band detection (Part 74): Theoretical and simulated performance

45 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 45 Probability of miss detection and false alarm

46 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 46 Detector Link Margin

47 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 47 PHY Presentation Outline Background Top-level description of modulation/coding Channel bonding Modulation Parameters Spreading OFDMA Sensing techniques OQAM/OFDMA Duo-binary CTC

48 doc.: IEEE /0105r1 Submission OFDM/OQAM Outline Principles of OFDM/OQAM The IOTA Waveform Advantages of OFDM/OQAM Simulation results

49 doc.: IEEE /0105r1 Submission OFDM/OQAM principles (1) Aim: to increase OFDM spectral efficiency by : –Removing the guard interval (cyclic prefix); –Delivering a sharper spectral signal than OFDM. How: The waveform that modulates OFDM sub- carriers should be as much as possible localized in time and frequency domains to minimize inter-symbol and inter-carrier interferences.

50 doc.: IEEE /0105r1 Submission OFDM/OQAM principles (2) However, the waveform must guarantee orthogonality between sub-carriers and multi-carrier symbols. –Appropriate waveform exist but guarantee orthogonality in the real domain  OffsetQAM modulation should be considered on each sub-carrier. Example: IOTA waveform (optimally localized in time and frequency).

51 doc.: IEEE /0105r1 Submission OFDM/OQAM principles (3) OFDM/QAM Transmitted signal: takes the complex value representing the transmitted encoded data sent on the mth sub-carrier at the nth symbol; and the basic functions are obtained by translation in time and frequency of a prototype function such as: With Rectangular function x used in OFDM has weak frequency localization. OFDM/OQAM Introduces a time offset between real and imaginary parts of symbols takes real values; And with

52 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 52 OFDM/OQAM principles (3) Time-frequency lattice

53 doc.: IEEE /0105r1 Submission The IOTA function (1) IOTA = Isotropic Orthogonal Transform Algorithm IOTA is a prototype function obtained by the orthogonalization of the Gaussian function Its particularity: the IOTA waveform modulating each sub-carrier is: – Quasi-optimally localized in both time and frequency – Isotropic: it has the same shape as its Fourier transform => delay spread and Doppler are both equally managed

54 doc.: IEEE /0105r1 Submission The IOTA function (2)

55 doc.: IEEE /0105r1 Submission The IOTA function (3) The IOTA function can be denoted by: Where: The transmitted signal is:

56 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 56 Advantages of OFDM/OQAM (1) Spectrum is sharper : 70 dB instead of 30 dB This feature helps to protect the adjacent channels

57 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 57 Advantage of OFDM/OQAM (2) Cyclic prefix not mandatory more useful bit-rate This extra bit-rate may be used to: –Increase the global net bit-rate of the system; –Increase the robustness and therefore the range, or decrease the power. Cyclic prefix1/41/81/161/32 Bit-rate OFDM/QAM 1/ Mbits/s13.5 Mbits/s14.47 Mbits/s14.95 Mbits/s Bit-rate OFDM/OQAM 1/ Mbits/s

58 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 58 Simulation results Simulation parameters: –Constellation : 64 QAM –Coding rate : ½ –Bandwidth : 7 MHZ –Channel: 641 MHz –Channel model: Profile A of WRAN

59 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 59 OFDM/OQAM vs OFDM/QAM with Convolutional FEC

60 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 60 OFDM/OQAM vs OFDM/QAM with Duo-binary Turbo-codes

61 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 61 State of the art OQAM waveform has been standardized by TIA committee TR8 for Private Land Mobile applications

62 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 62 PHY Presentation Outline Background Top-level description of modulation/coding Channel bonding Modulation Parameters Spreading OFDMA Sensing techniques OQAM/OFDMA Duo-binary CTC

63 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 63 Duo-binary Turbo-codes Outline Duo-Binary Turbo Codes Internal interleaver Flexibility Performance Simulations

64 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 64 Duo-Binary Turbo-codes Information bits are encoded by couples

65 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 65 Duo-Binary Turbo-code Duo-Binary input: two decoded bit output at a time –Reduction of latency and complexity per decoded bit (compared to Binary TC) –Better convergence Circular (tail-biting) encoding –No trellis termination overhead Original interleaving scheme –Larger minimum distances –Improved asymptotic performances

66 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 66 Internal Interleaver Algorithmic permutation –One equation, 4 parameters (P0, P1, P2, P3) –Parameters selected such that interleaver is contention-free Adjusting the TC to a blocksize only requires modification of the 4 parameters Quasi-regular permutation (easy connectivity) Inherent parallelism i = 0, …, N-1, j = 0,...N-1 level 1: if j mod. 2 = 0, let (A,B) = (B,A) (invert the couple) level 2: -if j mod. 4 = 0, then P = 0; -if j mod. 4 = 1, then P = N/2 + P 1 ; -if j mod. 4 = 2, then P = P 2 ; -if j mod. 4 = 3, then P = N/2 + P 3. i = P 0 *j + P +1 mod. N

67 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 67 Flexibility Can be easily adjusted to any blocksize –Storage of the 4 parameters for all blocksizes considered –Possibility of a generic approach (default parameters) All coding rates are possible –Through puncturing patterns –Natural coding rate is ½: increased robustness to puncturing Performance vs complexity: several adjustments are possible –Number of iterations, Decoding algorithm, … Implementation: interleaver enables different degrees of parallelism –Can be adjusted to meet complexity/throughput requirements

68 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 68 Flexibility The number of iterations can be adjusted for a better performance- complexity trade-off

69 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 69 Performance Duo-Binary TC, 8 iterations, Max-Log- MAP decoding IEEE e structured LDPC, BP decoding, 50 iterations AWGN, R=1/2, QPSK N=576 and 2304 (coded blocksize)

70 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 70 Short blocksize performance Hardware measurements Low BER (down to ) are achievable without error floor

71 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 71 Simulation results Simulation parameters –Constellation : 64 QAM –Coding rate : ½ –Bandwidth : 7 MHZ –Channel: 641 MHz –Channel model: Profile A of WRAN

72 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 72 Duo-binary Turbo-codes vs Convolutional with OFDM/QAM modulation

73 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 73 Duo-binary Turbo-codes vs Convolutional with OFDM/OQAM modulation

74 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 74 Advantages of Duo-binary Turbo-codes Good performance for a very wide range of blocksizes Highly flexible scheme, enabling a very fine granularity –Same encoder/decoder for all blocksizes/coding rates. –Several trade-off in performance (number of iterations, decoding algorithm), implementation complexity (degrees of parallelism). Reasonable complexity –Approximately 35% decrease in complexity per decoded bit compared to Binary TC.

75 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 75 State of the art Duo-binary Turbo-code is a mature technology This technology has already been selected by several standardization groups –IEEE / WiMAX; –DVB-RCS; –DVB-RCT; –ETSI HIPERMAN

76 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 76 Summary: Gains brought by OQAM and DTC OFDM/OQAM brings 10% more bit-rate –When converted in error protection enables to go from ¾ rate to 2/3 –Gain between 1 and 1,5 dB in C/N Duo-binary TC offers 3,5 to 4 dB When combined the gain is at least 4,5 dB that allows to increase the radius by 7,6 km (17%) with QPSK modulation in a Gaussian channel.

77 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 77 Final conclusion for WRAN PHY OFDMA/Channel bonding –Good answer to flexibility requirements Spreading QPSK –Captures multipath diversity and increases resiliency to interference (2-4 dB gain) OQAM waveform –Increases efficiency and incumbent protection Duo-binary Turbo-codes –Powerful error protection technique

78 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 78 Presentation Outline Introduction –A Glimpse of IEEE The Cognitive PHY Proposal The Cognitive MAC Proposal Conclusions

79 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 79 CMAC Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

80 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 80 CMAC Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

81 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 81 Introduction A Cognitive MAC (CMAC) layer is proposed to be used as the future IEEE MAC for WRANs Some aspects of CMAC have been inspired by the IEEE MAC standard However, major enhancements have been made –Support of multiple channel operation; –Coexistence with both incumbents and itself (self-coexistence); Measurements (incumbents and itself) Spectrum management (time, frequency and power) The Coexistence Beacon Protocol (CBP) Synchronization of overlapping BSs The Incumbent Detection Recovery Protocol (IDRP) Embedded wireless microphone beacon mechanism –Clustering support; etc.

82 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 82 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

83 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 83 Overview Given the very long propagation delays in WRANs, the BS regulates the medium access –Downstream: TDM (Time Division Multiplexing) –Upstream: DAMA (Demand Assigned Multiple Access) TDMA Packet Size: 50 bytesPacket Size: 1500 bytes

84 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 84 Overview (cont.) Combination of polling, contention and unsolicited bandwidth grants mechanisms Support of Unicast/Multicast/Broadcast for both management and data Connection-oriented MAC –Connection identifier (CID) is a key component –Defines a mapping between peer processes –Defines a service flow (QoS provisioning)

85 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 85 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

86 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 86 Protocol Stack Architecture Flexibility, scalability and efficiency are core elements Spectrum manager could be implemented in many ways

87 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 87 Protocol Stack Architecture (cont.) Flexible channel assignment –Implementers decide on the algorithm

88 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 88 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

89 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 89 Basic Terms and Definitions Superframe –Defined and delimited by a preamble and the SCH (superframe control header). It is comprised of a number of Frames Frame –Comprised of one DS and one US Subframe, where BS and CPEs use to communicate with each other Subframe –Formed by a number of Bursts Burst –Defined by a two dimensional segment of logical channel (frequency) and MAC slot (time). It may comprise of multiple MAC PDUs belonging to multiple CPEs MAC PDU –The smallest unit of transmission/reception by the MAC. It is comprised of the MAC header, the payload, and CRC

90 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 90 Motivation The problem –How to offer enhanced capacity and higher data rates? The fact –Spectrum occupancy measurements conducted by Shared Spectrum Company from January/2004 to August/2005 have shown that: “There is a significant amount of spectrum available in continuous blocks that are 1 MHz and wider ” “A dynamic spectrum sharing radio with a low agility, contiguous waveform will provide high utility” The solution –Simultaneous use of multiple contiguous TV channels

91 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 91 Superframe Structure Superframe Control Header (SCH) TV channels being bonded Coexistence and superframe information Number and size of frames Information on periodic quiet periods ID an transmit power of transmitter Location configuration information

92 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 92 Frame Structure CMAC is based on a TDD frame structure –Reduced complexity –In general, less measurements overhead –The flexible architecture (with the Spectrum Manager) already brings with it aspects of FDD The CMAC frame structure is comprised of two parts –A predominantly downstream (DS) subframe –An upstream (US) subframe

93 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 93 Frame Structure (cont.)

94 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 94 Time/Frequency Structure of a MAC Frame

95 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 95 Network Entry and Initialization The key problem

96 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 96 Downstream (DS) Transmissions DS = core messages + data (transmitted in bursts) –Two core DS messages: DCD and DS-MAP –Bursts identified by DIUC (Downstream Interval Usage Code) –Each burst may contain data for several CPEs DCD (Downstream Channel Descriptor) –Establishes association between DIUC and actual PHY parameters (e.g., modulation and coding) DS-MAP (Downstream map) –Defines the usage (i.e., scheduling) of the downstream –Critical, hence first message in each frame –For self-coexistence purposes, the BS may choose to use part of DS subframe for CBP protocol operation

97 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 97 Upstream (US) Transmissions US = core messages + data (contention and bursts) –Two core DS messages: UCD and US-MAP –Bursts identified by UIUC (Upstream Interval Usage Code) –The upstream can be segmented into several UIUC Contention-based –Initialization, Bandwidth Request, Urgent Coexistence Situation (UCS), CBP slots (SCS) Data Bursts UCD (Upstream Channel Descriptor) –Establishes association between UIUC and actual PHY parameters (e.g., modulation and coding) US-MAP (Upstream map) –Defines the usage (i.e., scheduling) of the upstream –Contains “grants”addressed to a particular CPE or a set of CPEs (e.g., for self-coexistence)

98 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 98 Bandwidth Management: Request/Grant Scheme Self correcting –No acknowledgement –All errors are handled the same way (i.e., periodic aggregate requests) Bandwidth requests –Are always per connection –Can specify DS/US Traffic Constraint IEs for better self-coexistence Bandwidth grants –Can be either per connection or per CPE –Grants (given as durations) are carried in US-MAP messages –CPE converts time into amount of data using information about the UIUC

99 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 99 Scheduling Services Unsolicited Grant Services (UGS) –For CBR and CBR-like flows (T1/E1) –No specific bandwidth request issued by CPE Real-time Polling Service (rtPS) –For rt-VBR-like service flows such as MPEG video –CPEs are polled to meet delay requirements Non-real-time Polling Service (nrtPS) –For non-real-time flows with better than best effort service such as bandwidth-intensive file transfer –CPEs are polled and can use contention interval Best Effort (BE) –E.g., Web surfing –CPEs use contention interval only

100 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 100 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

101 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 101 Coexistence Two primary types –With incumbents (TV service and Part 74 devices) –With other overlapping cells Self-Coexistence Measurements can be classified as: –In-band In case of incumbents, requires quiet periods (QP) –Out-of-band No need for quiet periods Coexistence is achieved by a joint application of: –Spectrum management (frequency and power) –“Interference-free” traffic scheduling (time)

102 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 102 Measurements Measurements form a key component of CMAC –Protection of incumbents and self-coexistence The BS may request multiple measurements in a single management message –E.g., ATSC, DVB, Wireless Microphone, Measurement messages may be transmitted through multicast –Allows the implementation of advanced features such as clustering –Bandwidth efficient

103 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 103 Measurements (cont.) Bulk Measurement Request (BLM-REQ) –Transmitted by the BS to CPEs –Includes information such as Channels to measure Multiple single measurement requests Bulk Measurement Response (BLM-RSP) –Transmitted by CPE to BS –If needed, acknowledges the receipt of the BLM-REQ message Bulk Measurement Report (BLM-REP) –Transmitted by CPE to BS –Returns multiple single measurement reports Bulk Measurement Acknowledgement (BLM-ACK) –Transmitted by BS to CPE –Acknowledges receipt of measurement report

104 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 104 Measurements (cont.) Single measurements can be of various types –Signal specific measurement request TV system and Wireless microphones –Beacon measurement request CBP, BS, and Wireless microphone beacons –CPE statistics measurement request –Stop measurement request –Location configuration measurement request A range of parameters can be specified

105 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 105 Measurements (cont.) There is almost a one-to-one correspondence between measurement requests and reports Some of the individual reports are: –Signal specific measurement report TV/Wireless Microphone system type, measured value, precision, etc. –Beacon measurement report Information on any CBP, BS, or Wireless microphone beacons received –CPE statistics measurement report E.g., Packet error rate –Location configuration measurement report If known, location information (GPS, triangulization, and so on)

106 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 106 Channel Management Channel management is key to effective network coordination, coexistence and sharing Included in two modes –Embedded –Non-embedded A set of messages are defined to allow flexible management of channels, including: –Add/remove channel(s) to/from current set of channels –Switch channel(s) of operation –Quiet selected channel(s) – possibly to perform in-band measurement

107 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 107 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

108 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 108 Coexistence with Incumbents Accomplished through the following steps: –Measurements (discussed earlier) –Detection TV: For more info, please see PHY proposal. Wireless Microphones –PHY solution: For more info, please see PHY proposal. –MAC solution: See next slide. –Incumbent Notification –Incumbent Detection Recovery

109 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 109 Coexistence with Incumbents Accomplished through the following steps: –Measurements (discussed earlier) –Detection TV: For more info, please see PHY proposal. Wireless Microphones –PHY solution: For more info, please see PHY proposal. –MAC solution: See next slide. –Incumbent Notification –Incumbent Detection Recovery

110 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 110 MAC Layer Detection of Wireless Microphones From the transmitter perspective, wireless microphone beacons (WMB) can be of two types –Embedded device which has the additional capability of emitting WMBs –Non-embedded Currently addressed by the Part 74 Study/Task Group Based on the proposed MAC layer, we have developed an embedded WMB approach that: –Reliably detects multiple collocated networks –Upon sending WMBs, this mechanism causes minimal, if any, harmful interference to collocated networks –Once either BSs or CPEs detect the WMB, a dissemination is made and all present networks vacate the channel

111 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 111 Incumbent Notification The problem –How to notify the BS about the presence of incumbents in a timely fashion? Two solutions are possible –CPEs with upstream bandwidth allocation Send report provided bandwidth and time are available; and/or Set dedicated bits in MAC header –CPEs without upstream bandwidth allocation Urgent Coexistence Situation (UCS) Notification slots reserved specifically for incumbent notification purposes –Can use either contention-based or contention-based CDMA access The size of a slot fits the smallest MAC frame necessary to perform the incumbent notification

112 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 112 Incumbent Notification (cont.)

113 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 113 Incumbent Notification (cont.) The BS can use various strategies depending upon how reliable it wants the notification to be –Trade-off between overhead and data efficiency –Scalability

114 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 114 Incumbent Detection Recovery The problem –How does the cell recover from an UCS with incumbents in a timely fashion?

115 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 115 Incumbent Detection Recovery (cont.) The Incumbent Detection Recovery Protocol (IDRP) –Introduces the concept of Backup Channel –The network not only performs in-band measurements, but also out-of-band measurements Out-of-band measurements will determine a suitable Backup Channel –The network falls back to the Backup Channel in case communication is preempted by an incumbent –The algorithms at both the BS and CPEs are provided These algorithms also account for the case when no Backup Channel is available

116 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 116 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

117 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 117 Self-Coexistence The general problem TDMA Schedule

118 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 118 Self-Coexistence (cont.) Indeed a major issue –E.g., h Becomes even more critical in given –The large coverage range –Its unlicensed nature Directional antennas at CPEs do not address the problem

119 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 119 Self-Coexistence (cont.) Some approaches to better self-coexistence –Over the backhaul Pros – can wash its hands (throw the “hot potato” to somebody else) Cons –Will there be really a “common backhaul” between competing WISPs? Can rely on that? –What if this “common backhaul” is down? –Can rely on the “upper layers” to take care of self-coexistence? –Coordination is an active process (e.g., quiet periods), and not a “once-in-a-month thing” –Over-the-air Pros –Built-in and self-healing system Cons –More complex MAC layer (but just a little more)

120 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 120 Self-Coexistence (cont.) Two solutions are proposed –BS beacon based –The Coexistence Beacon Protocol (CBP) Both solutions: –Can be implemented either over-the-air or via a backbone Here, we focus on the over-the-air implementation –Allow either one-way or two-way (i.e., negotiation) communication The BS and its CPEs shall participate in the self- coexistence task

121 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 121 Self-Coexistence (cont.) BS beacon based –Implemented through overheard BS beacons –BS beacons carry various information: Channels used Quiet periods Frame information Transmit power level –If needed, can use sensing antenna for this purpose –Allows better TPC and sharing in frequency only Case 1: Case 2:

122 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 122 Self-Coexistence (cont.) Coexistence Beacon Protocol (CBP) –CBP is executed by CPEs but under BS control –CPEs transmit coexistence packets carrying two types of information About the cell About a CPE’s reservations with the BS –Allows better TPC and sharing in both frequency and time CBP beacon

123 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 123 Self-Coexistence (cont.)

124 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 124 But what does the CPEs do with this information? If previously requested by the BS, report it Future upstream bandwidth reservation requests can contain time allocation constraints –For example, a CPE can specify: “Give me 100Kb of airtime, but not between T 1 and T 2 ” Note on the BS –Traffic Constraint (TRC-REQ/RSP) management messages are also available to the BS For example, can be used before the BS allocates any time for the CPE Allow the BS to inquire CPE about possible time allocation constraints

125 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 125 Then, what does the BS do about all this? If possible and desirable, avoid each other by switching channels Better TPC Implement “interference-free” scheduling –Sharing in time and frequency

126 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 126 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

127 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 127 Synchronization of Overlapping BSs The problem –Frames of co-channel overlapping BSs are asynchronous, which makes coexistence even harder Numerous benefits to synchronization –Incumbent protection Quiet period synchronization of overlapping BSs Improved detection –Self-Coexistence Logical channel amongst overlapping BSs Efficient sharing of resources BS 1 : BS 2 : Time

128 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 128 Synchronization of Overlapping BSs (cont.) Synchronization is proposed amongst multiple collocated networks

129 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 129 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

130 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 130 Clustering Alleviate much of the redundancy involved in the execution of the coexistence mechanisms –So, very suitable for –Can be employed in all coexistence mechanisms, except for the protection of Wireless Microphone services Based on key observations –Sensing outcome of close-by CPEs are likely to be “similar” –CPEs are stationary It is a two-step process conducted by the BS –Formation of Physical Cluster –Formation of Logical Cluster

131 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 131 Clustering: Physical Cluster (cont.) Creation of Physical Clusters is totally localized at the BS –No direct involvement from CPEs The BS groups together CPEs sensing “similar” characteristics of the incumbent signal –Could also be based on location relative to the incumbent transmitter

132 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 132 Clustering: Physical Cluster (cont.) Based on the well-known k- means clustering algorithm The algorithm –Initially, no clustering –CPEs report measurements to the BS (BLM-REP) which constructs incumbent profiles –Then, the BS runs the clustering algorithm

133 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 133 Clustering: Logical Cluster (cont.) Formed by CPEs belonging to different Physical Clusters Allows the BS to group those CPEs that are less likely to contend for the same airtime CPEs within a Logical Cluster perform the same “coexistence task”

134 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 134 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

135 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 135 Security Sublayer Based on IEEE e/D12 security sublayer –Generic security framework made specifically for BWA networks –Meets all the security requirements identified for the WRAN Standard –Deeply studied and improved by various security experts (including IEEE and IETF ones) Composed of two sublayers –A Privacy Key Management protocol (PKM) which provides authentication, authorization and secure key distribution between the BS and the CPE –An encapsulation protocol which provides data packets protection

136 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 136 Security Sublayer (cont.) Mutual Authentication of the devices –Either using RSA and digital certificates –Or using EAP and EAP-method specific credentials Authentication of the subscribers (optional) –Using EAP and EAP-method specific credentials Authorization based on authenticated CPE and/or subscriber identity –Give access to dedicated service flows

137 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 137 Security Sublayer (cont.) Data packets encryption –Using strong cryptographic algorithms (AES) Management frames integrity protection –Using keyed message authentication codes Protection against Deny of Service and other attacks –Protection of management frames against forgery and replay attacks –Protection of data frames against replay attacks –Protection of EAP packets during subscribers authentication –Protection of every key negotiation phase, using digital signatures and random numbers

138 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 138 Presentation Outline Introduction The CMAC Protocol –Architecture –Data communication Superframe and Frame Structures Network entry and initialization Downstream and Upstream scheduling –Coexistence Incumbents Self-Coexistence Synchronization of overlapping BSs Clustering –Security Performance Evaluation

139 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 139 Performance Evaluation All aspects of CMAC are being implemented in OPNET –OPNET is considered the most well-reputated and reliable network simulation tool available today In all simulations: –In case of quiet periods (QP), every CPE performs detection in all in-band channels (e.g., N-1, N, and N+1 in case of a single TV channel) –DFS model is implemented as per the requirements document –No fragmentation or packing Some common simulation parameters –Superframe size = 12 frames, where Frame size = 40 ms –Packet size = 1 Kbyte –Detection time per TV channel = 13 ms –64-QAM rate 2/3 and Symbol time = 310 µs

140 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 140 Throughput at the MAC SAP Evaluate the throughput of CMAC under varying number of bonded TV channels 1 BS and 127 CPEs

141 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 141 Throughput at the MAC SAP (cont.) Impact of QP on throughput is more confined to high load scenarios –The scheduler can properly handle this Channel bonding provides significant performance improvement

142 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 142 Channel Efficiency Evaluate the channel utilization –The overall impact of QPs is only noticeable in high loads Fragmentation and packing can improve these figures even more

143 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 143 Network Joining Time Evaluate, for the worst case scenario, the average network joining time by a CPE –CPEs first scan channel for a time equivalent to a frame size –CPE stays in a channel for a superframe duration after that –This is followed by network entry and initialization More efficient algorithms can be easily implemented

144 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 144 Network Joining Time (cont.) 1 BS and 127 CPEs –BS is powered up at simulation startup –CPEs power up at random times FRD requires joining time under 10 sec

145 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 145 Impact on QoS Evaluate the impact of quiet periods and incumbents on QoS Traffic pattern –A total of 3 Mbps constant aggregate US traffic –DS traffic varies between 3 Mbps and 15 Mbps All 127 CPEs establish connections with BS –Out of these, 4 real time (QoS) connections at 32 Kbps each –Other connections are BE or non- real time

146 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 146 Impact on QoS (cont.) The overall impact on average downstream delay is very small –QoS can be satisfied to a large extent (sec) Effect of Queuing

147 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 147 Impact on QoS (cont.) The overall impact on average upstream delay is not so small as in the downstream case –Despite of that, QoS can still be satisfied to a significant extent (sec)

148 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 148 Handling of Incumbents Evaluate the detection, notification and recovery capability of CMAC 1 BS and 9 CPEs TV station starts in-band operation at a random time –Incumbent is detected during quiet period

149 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 149 Handling of Incumbents (cont.) Network operation is quickly restored –BS and unaffected CPEs switch to Backup Channel –CPEs who do not receive switch message go to Backup Channel after timeout (2 frames) Channel AChannel B

150 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 150 Handling of Incumbents (cont.) Evaluate the dynamics of channel bonding –Together with handling of incumbents –Network can switch to one or more Backup Channel Channel AChannel B

151 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 151 Presentation Outline Introduction –A Glimpse of IEEE The Cognitive PHY Proposal The Cognitive MAC Proposal Conclusions

152 doc.: IEEE /0105r1 Submission November 2005 Carlos Cordeiro, PhilipsSlide 152 Conclusions Proposed a PHY and MAC that addresses the requirements set forth by the WG PHY –Based on OFDMA Spreaded OFDMA O-QAM –Flexible channel configurations (6, 12, and 18 MHz) –TV and Part 74 detection MAC –Coexistence is a key feature Incumbent protection Self-coexistence –CBP and IDRP protocols, superframes, support of channel bonding, etc.


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