Future Work

At the end of this dissertation, several analyses are suggested to be further study to make current research results become more complete and stronger. The first one is the analysis of VLSI architecture of FD symbol synchronizer. Since the proposed architecture uses higher clock speed to achieve more hardware sharing, the tradeoff between silicon area and power consumption should be further analyzed. The second one is the computation complexity of the proposed pre-pruning K-best scheme can be analyzed deeply and compared with other advance K-best algorithms. To extend the related research topics, a number of open issues are also summarized as follows:

1. For the evolution of IEEE 802.11 WLAN standards, the next generation WLAN communication systems are defined in the amendments of IEEE 802.11ac and IEEE 802.11ad. IEEE 802.11ac can be viewed as the BW extension version from IEEE 802.11n. Therefore, most IEEE 802.11n receiver modules can still be reused with slight modifications to the IEEE 802.11ac receiver architecture. However, IEEE 802.11ad enables the multi-Gbps Wi-Fi via a new 60G PHY. The longer

preamble length (i.e. Golay codes) and symbol block size (i.e. Reed Solomon code in SC mode) significantly increase the complexity of the proposed frequency-domain synchronization and equalization. Moreover, high sampling rate also leads critical VLSI implementations. To realize the FD receiver in IEEE 802.11ad will be therefore a very challenge topic in the future research efforts.

2. In this dissertation, we design a single-channel WMNs. The robustness of routing protocol is what we consider firstly. Therefore, the broadcasting strategies for broadcast-type control frames are evaluated. However, the co-channel interference avoidance is another important issue which significantly degrades the network capacity. The multi-channel WMNs may suppress the effect of co-channel interference, but it introduces the adjacent channel interference and makes protocol complex. Recently, the MIMO spatial multiplexing scheme has been applied to reduce the con-channel interference. Moreover, the new coming standard, IEEE 802.11ac, invites the scheme of multi-user (MU)-MIMO, which allows multiple receivers transfer data to single transmitter in up-link way or single transmitter transfers data to multiple receivers in down-link way. This scheme can significantly reduce the co-channel interference and increase the system capacity in single-channel WMN. Therefore, the integration of MU-MIMO scheme into our WMN becomes an emergent and meaningful topic. It also needs

to highlight that this topic includes interference mulling, MU-MIMO scheduling and fairness problem, which should be designed with cross-layer over physical, media access control (MAC), and even application layers.

3. Mobile communication systems have also evolved rapidly in the last decade. The 3^rd Generation Partnership Project (3GPP) has submitted the Long Term Evolution-Advance (LTE-A) to International Telecommunication Union Telecommunication Standardization Sector (ITU-T) as a candidate 4G system in late 2009. One of the new concept in LTE-A is the coordinated multipoint (CoMP) transmission, which enables Multiple base stations cooperate to determine the scheduling, transmission parameters, and transmit antenna weights for a particular user equipment. Unlike the conventional synchronization algorithm focus on point-to-point transmission, the synchronization in CoMP becomes an interesting topic since the received data may come form multiple cooperative stations.

Reference

[1] IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Nov. 1997. P802.11.

[2] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std 802.11b, 1999.

[3] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std 802.11a, 1999.

[4] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std 802.11g, 2003.

[5] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Enhancements for Higher Throughput, IEEE Std 802.11n, 2009.

[6] D. Falconer, and S. L. Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson,

“Frequency domain equalization for single-carrier broadband wireless systems,”

IEEE Commun. Mag., vol. 40, pp. 58-66, Apr. 2002.

[7] Z. Wang, X. Ma, and G. B. Giannakis, “OFDM or single-carrier block transmissions?,” IEEE Trans. Commun., vol. 52, pp. 380-394, March 2004.

[8] I. F. Akyildiz, X. Wang, and W. Wang, “Wireless Mesh Networks: A Survey,”

Comp. Net., vol. 47, no. 4, 2005, pp. 445–87.

[9] R. Bruno, M. Conti, and E. Gregori, “Mesh Networks: Commodity Multihop Ad Hoc Networks,” IEEE Commun. Mag., vol. 43, no. 3, Mar. 2005, pp. 123–31.

[10] Y-D. Lin and Y-C. Hsu, “Multihop Cellular: A New Architecture for Wireless Communications,” in Proc. IEEE INFOCOM, vol.3, no., pp.1273-1282 vol.3, 26-30 Mar 2000.

[11] J. Bicket et al., “Architecture and Evaluation of an Unplanned 802.11b Mesh Network,” in Proc. ACM Mobi-Com, 2005.

[12] A. Raniwala and T. Chiueh, “Architecture and Algorithms for an IEEE 802.11-based Multi-Channel Wireless Mesh Network,” in Proc. IEEE INFOCOM, vol.3, no., pp. 2223- 2234 vol. 3, 13-17 March 2005.

[13] K. Ramachandran et al., “On the Design and Implementation of Infrastructure Mesh Networks,” in Proc. IEEE Wksp. Wireless Mesh Net., 2005.

[14] IEEE P802.11s/D2.03, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications — Amendment: Mesh Networking,” Nov.

2008.

[15] A. Baschirotto, R. Castello, F. Campi, G. Cesura, M. Toma, R. Guerrieri, R. Lodi, L. Lavagno, and P. Malcovati, "Baseband analog front-end and digital back-end for reconfigurable multi-standard terminals," IEEE Circuits and Systems Magazine, vol.6, no.1, pp. 8- 28, 2006.

[16] T. Shono, Y. Shirato, H. Shiba, K. Uehara, K. Araki, M. Umehira, "IEEE 802.11 wireless LAN implemented on software defined radio with hybrid programmable architecture," IEEE Trans Wireless Commun., vol.4, no.5, pp. 2299- 2308, Sept.

2005

[17] J. L. Hennessy and D. A. Patterson, Computer Architecture: A Quantitative Approach, Morgan Kaufmann Publishers, 3rd Edition, 2003.

[18] Shin-Yuan Wang, and Chia-Chi Huang, "On the architecture and performance of an FFT-based spread-spectrum downlink RAKE receiver," IEEE Trans. Veh.

Tech., vol.50, no.1, pp.234-243, Jan 2001.

[19] P. K. Prakasam, M. Kulkarni, Xi Chen, Yu Zhuizhuan, S. Hoyos, J.

Silva-Martinez, and E. Sanchez-Sinencio, "Applications of multipath transform-domain charge-sampling wide-band receivers," IEEE Trans. Circuits Syst. II, vol.55, no.4, pp.309-313, Apr. 2008.

[20] S. Hoyos, B. M. Sadler, and G. R. Arce, “Broad-band multicarrier communications receiver based on analog to digital conversion in the frequency domain,” IEEE Trans. Wireless Commun., vol. 5, no. 3, pp. 652–661, Mar. 2006.

[21] Gernot Hueber, and Robert Bogdan Staszewski, Multi-Mode / Multi-Band RF Transceivers for Wireless Communications: Advanced Techniques, Architectures, and Trends. Wiley-IEEE Press, November 2010.

[22] S. Hoyos, S. Pentakota,Yu Zhuizhuan,E.S.A. Ghany, Chen Xi, R. Saad, S.

Palermo,J. Silva-Martinez, "Clock-Jitter-Tolerant Wideband Receivers: An

Optimized Multichannel Filter-Bank Approach," IEEE Trans. Circuits Syst. I, vol.58, no.2, pp.253-263, Feb. 2011.

[23] S. Hoyos, and B. M. Sadler, “UWB mixed-signal transform-domain direct-sequence receiver,” IEEE Trans. Wireless Commun., vol. 6, no. 8, pp.

3038-3046, Aug. 2007.

[24] J.-J. van de Beek, M. Sandell, and P. O. Borjesson, “ML estimation of time and frequency offset in OFDM systems,” IEEE Trans. Signal Process., vol. 45, no. 7, pp. 1800–1805, Jul. 1997.

[25] H. Minn, V. K. Bhargava, and K. B. Letaief, “A robust timing and frequency synchronization for OFDM systems,” IEEE Trans. Wireless Commun., vol. 2, no.

4, pp. 822-839, Jul. 2003.

[26] A. J. Coulston, “Maximum likelihood synchronization for OFDM using a pilot symbol: algorithms,” IEEE J. Sel. Areas Commun., vol. 19, no. 12, pp.

2486-2494, Dec. 2001.

[27] E. Sourour and G. E. Bottomley, “Effect of frequency offset on DS-SS acquisition in slowly fading channels,” in Proc. IEEE Wireless Communications and Networking Conf., vol. 2, New Orleans, LA, Sept. 1999, pp. 569–573.

[28] A. Fort, J.-W. Weijers , V. Derudder , W. Eberle and A. Bourdoux "A performance and complexity comparison of auto-correlation and cross-correlation for OFDM burst synchronization", in Proc. IEEE ICASSP, vol. 2, pp. 341 2003.

[29] F. Tufvesson, O. Edfors, and M. Faulkner, “Time and frequency synchronization for OFDM using PN-sequence preambles,” in Proc. IEEE VTC., vol. 4, pp.

2203–2207, 1999.

[30] K. W. Yip, Y. C. Wu, and T. S. Ng, “Timing-synchronization analysis for IEEE 802.11a wireless LANs in frequency-nonselective Rician fading environments,”

IEEE Trans. Wireless Commun., vol. 3, pp. 387-394, Mar. 2004.

[31] E. G. Larsson, G. Liu, J. Li, and G. B. Giannakis, “Joint symbol timing and channel estimation for OFDM based WLANs,” IEEE Commun. Lett., vol. 5, no.

8, pp. 325-327, Aug. 2001.

[32] Y.-C. Wu, K.-W. Yip, T.-S. Ng and E. Serpedin, “Maximum-likelihood symbol synchronization for IEEE 802.11a WLANs in unknown frequency-selective fading channels,” IEEE Trans. Wireless Commun., vol. 4, pp. 2751, Nov. 2005.

[33] J. Terry, and J. Heiskala, OFDM Wireless LANs: A Theoretical and Practical Guide, Indianapolis, Indiana., Sams, 2002.

[34] P.A. Dmochowski, and P.J. McLane, “Frequency domain equalization for high data rate multipath channels,” in Proc. IEEE Pacific Rim Conf., vol.2, pp.534~537, Aug., 2001.

[35] J.J. Shynk, “Frequency-domain and multirate adaptive filtering,” IEEE Signal Process. Mag., vol.9, Issue 1, Jan., 1992.

[36] T. D. Chiueh and P. Y. Tsai, OFDM Baseband Receiver Design for Wireless Communications. Wiley, September 2007.

[37] P.W. Wolniansky, G.J. Foschini, G.D. Golden, and R.A. Valenzuela, “V-BLAST:

An architecture for realizing very high data rates over the rich-scattering wireless channel,” in Proc. IEEE ISSSE, pp.295–300, Sept. 1998.

[38] X. Zhu and R. D. Murch, “Performance analysis of maximum likelihood detection in a MIMO antenna system,” IEEE Trans. Commun., vol. 50, pp.

187–191, Feb. 2002.

[39] E. Viterbo and J. Boutros, “A universal lattice code decoder for fading channels,”

IEEE Trans. Inf. Theory, vol.45, no.5, pp.1639–1642, July 1999.

[40] Kwan-wai Wong; Chi-ying Tsui; Cheng, R.S.-K.; Wai-ho Mow; , "A VLSI architecture of a K-best lattice decoding algorithm for MIMO channels," in Proc.

ISCAS, vol.3, no., pp. III-273- III-276 vol.3, 2002.

[41] Zhan Guo, and Nilsson, P.; , "A VLSI architecture of the Schnorr-Euchner decoder for MIMO systems," in Proc. ISCAS, vol.1, no., pp. 65- 68 Vol.1, 2004.

[42] Mondal, S., Salama, K.N., and Eltawil, A., "On the VLSI Implementation of low complexity K-best MIMO decoders," in Proc. ICM, vol., no., pp.337-340, 2008.

[43] Higuchi, K.; Kawai, H.; Maeda, N.; Sawahashi, M.; , "Adaptive selection of surviving symbol replica candidates based on maximum reliability in QRM-MLD for OFCDM MIMO multiplexing," in Proc. GLOBECOM, vol.4, no.,

pp. 2480- 2486 Vol.4, 2004.

[44] L. Hideki et al., “Evaluating the Impact of RTS-CTS in OLPC’s XOs’ Mesh Networks,” in Proc. SBrT, 2007.

[45] D. Koutsonikolas, J. Dyaberi, P. Garimella, S. Fahmy, Y.C. Hu, “On TCP throughput and window size in a multihop wireless network testbed,” in Proc.

WiNTECH07, Sep. 2007, Montreal, Quebec, Canada.

[46] Y. Sun, I. Sheriff, E.M. Belding-Royer, K.C. Almeroth, “An experimental study of multimedia traffic performance in mesh networks,” in Proc. WitMeMo, 2005 [47] K. Chebrolu, B. Raman, S. Sen, “Long-distance 802.11b links: performance

measurements and experience,” in Proc. MOBICOM, 2006.

[48] D. Gokhale, S. Sen, K. Chebrolu, B. Raman, “On the feasibility of the link abstraction in (rural) mesh networks,” in Pro. INFOCOM, 2008, pp.61–65.

[49] J. Camp, J. Robinson, C. Steger, E. Knightly, “Measurement driven deployment of a two-tier urban mesh access network,” in Proc. ACM MobiSys, June 2006, pp.

96–109.

[50] A. Arjona, C. Westphal, J. Manner, A. Yla-Jaaski, S. Takala, “Can the current generation of wireless mesh networks compete with cellular voice?,” in Proc.

Elsevier ComCom Journal, pp.1564-1578, vol. 31, Issue 8, May 2008.

[51] A. Burg, M. Borgmann, M. Wenk, M. Zellweger, W. Fichtner, and H. Bolcskei,

“VLSI implementation of MIMO detection using the sphere decoding algorithm,” IEEE J., Solid-State Circuits, vol.40, no.7, pp. 1566-1577, July 2005.

[52] Part 15.3: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPANs):

Amendment 2: Millimeter-Wave Based Alternative Physical Layer Extension, IEEE 802.15.3c, Oct. 2009.

[53] IEEE 802.11ad Task Group, 2010. [Online]. Available:

http://www.ieee802.org/11/Reports/tgad update.htm

[54] J. Proakis and D. Manolakis, Digital Signal Processing: Principles, Algorithm, and Applications, 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 1996.

[55] B. O’Hara, and A. Petrick, IEEE 802.11 Handbook: A Designer’s Companion,

IEEE Press, 2nd Edition, 2005.

[56] V. Erceg, et al., TGn channel models, IEEE 802.11-03/940r4, May, 2004.

[57] T. Y. Hsu, B. J. Shieh, and C. Y. Lee, “An all-digital phase-locked loop (ADPLL) based clock recovery circuits,” IEEE J. Solid-State Circuits, vol. 34, pp.

1063-1073, Aug. 1999.

[58] C. C. Chung and C. Y. Lee, “An all-digital phase-locked loop for high-speed clock generation,” IEEE J. Solid-State Circuits, vol. 38, pp. 347-351, Feb. 2003.

[59] M. Krstic, A. Troya, K. Maharatna, and E. Grass, "Optimized low-power synchronizer design for the IEEE 802.11a standard,” in Proc. ICASSP '03, vol.2, no., pp. II- 333-6 vol.2, 6-10, 2003.

[60] T.-H. Kim, and I.-C. Park, "Low-Power and High-Accurate Synchronization for IEEE 802.16d Systems," IEEE Trans. VLSI, vol.16, no.12, pp.1620-1630, Dec.

2008.

[61] H.-Y. Liu; C.-Y. Lee, "A Low-Complexity Synchronizer for OFDM-Based UWB System," IEEE Trans. Circuits Syst. II, vol.53, no.11, pp.1269-1273, Nov. 2006.

[62] B. M. Baas, "A low-power, high-performance, 1024-point FFT processor", IEEE J. Solid-State Circuits, vol. 34, no. 3, pp. 380 - 387, 1999.

[63] A. Chun, E. Tsui, I. Chen, H. Honary, and J. Lin, “Application of the Intel@

Reconfigurable Communication Architecture to 802.11a, 3G and 4G Standards,”

in Proc. IEEE Symp. Emerging Technol., May, 2004. pp.659~662.

[64] J. Hoffman, D. A. Ilitzky, A. Chun, and A. Chapyzhenka, “Architecture of the Scalable Communications Core,” in Proc. IEEE Symp. Networks-on-Chip, 2007, pp. 40–52..

[65] J.H. Jang, H.C. Won, and G.H. Im, “Cyclic Prefixed Single Carrier Transmission with SFBC over Mobile Wireless Channels,” IEEE Signal Process, Lett., vol.13, no.5, pp.261~264, May, 2006.

[66] M. Morelli, L. Sanguinetti, and U. Mengali, “Channel Estimation for Adaptive Frequency-Domain Equalization,” IEEE Trans Wireless Commun., vol.4, no.5, pp.2508~2518, Sep., 2005.

[67] Y. Zhu, and K.B. Letaief, “Single Carrier Frequency Domain Equalization with