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1 Efficient Adaptive Modulation Technique for MAC-PHY Cross Layer Optimization in OFDMA-based Cellular Systems An adaptive transmission scheme using QAM and LDPC code is proposed for an OFDMA cellular system employing FDD. Also, adaptive algorithms for active user selection, subchannel transmission power allocation, and modulation and coding set selection were proposed. The performance of the proposed scheme was obtained from computer simulation and was compared with that of the conventional scheme using mean SNR only. It is shown that the proposed scheme can provide up to 5.0dB gain over the conventional scheme at the expense of only 3 more bits in feedback information. Keywords: Adaptive Transmission, OFDMA, LDPC I

2 II

3 P pilot III

4 x x k k yahxn, (1)

5 A 2 h n 2 σ 2 zz i jz q zh * yhahxn', (2) n'h * nh 2 σ 2 z Ahx 2 σ 2 x 0 Λ(x 0 ) Λ(x 0 )log ( Σ Pr{zh,x}Pr{x} ) log ( Σ Pr{zh,x}Pr{x} ) xx 0,0 xx 0,1 (z i v) 2 (z q v) 2 (z i v) 2 (z q v) 2 log ( exp ( ) exp ( 2σ )) 2 2σ 2 (z i v) 2 (z q v) 2 (z i v) 2 (z q v) 2 log ( exp ( ) exp ( )), 2σ 2 2σ 2 (z i v) 2 (z i v) 2 2σ 2 2σ 2 2vz i (3) σ 2 X k,l k l vah2x 0 0z i v σ 2 Λ(x 0 ) 2v 2 σ 2 A 2 h 2 σ 2 4v 2 σ 2 2A 2 h 2 σ 2 Λ(x 1 ) L h l, l0,... L1 1 L2 A 2 h l 1 E{Λ(x k )x k 0} Σ 2m SNR L l0 σ 2 1 L1 2A 2 h l 2 A 4 h l 4 E{Λ 2 (x k )x k 0} Σ ( ) L l0 σ 2 σ 4 Var{Λ(x k )x k 0}E{Λ 2 (x k )x k 0}E 2 {Λ(x k )x k 0} 1 L1 2A 2 h l 2 A 4 h l 4 Σ ( L l0 σ ) 2 σ 4 1 L1 A 2 h l 2 ( Σ ) 2 L l0 σ 2 1 L1 2A 2 h l 2 1 L1 A 2 h l 2 2 Σ Σ ( L l0 σ ) 2 L l0 σ 2 1 L1 A 2 h l 2 2 ( Σ L l0 σ ) 2 4m SNR 4σ 2 SNR, (4)

6 m SNR σ 2 SNR 1 L1 A 2 h l 2 m SNR Σ, L l0 2σ 2 1 L1 A 2 h l L1 A 2 h l 2 2 σ 2 SNR Σ ( ) ( Σ ). (5) L l0 2σ 2 L l0 2σ Λ(x 0 )log ( Σ Pr{zh,x}Pr{x} ) xx 0,0 log ( Σ Pr{zh,x}Pr{x} ) xx 0,1 log(max xx 0,0 Pr{zh,x}Pr{x}) log(max xx 0,1 Pr{zh,x}Pr{x}) Euclidean distance differenceσ 2. (6) A 2 h 2 A 2 h 2 σ 2 E{Λ(x k )x k 0} m SNR Var{Λ(x k )x k 0} am SNR bm 2 SNR cσ 2 SNR (7)

7 σ SNR σ SNR m SNR IV m SNR σ SNR l P pilot m l,snr σ l,snr l P pilot K1(0,...,K) k

8 SNR k k (σ SNR ) l k P l,k P l,k P pilot SNR k m l,snr k (σ l,snr ) (8) SNR k k (σ SNR ) P c l,k P c l,k P pilot SNRc k m l,snr (9) SNR c k k S k * arg max r(k) subject to P 1,k P A,Max (10) k r(k) k P A,Max X P A,Max P S,Max P A,Max S l

9 k(l)arg max r(k) subject to P l,k P S,Max (11) k S l * (s)s1s k(l * (s)) for s1:s l * (s)arg max k(l); k(l * (s))0; l end for (12) X P S,Max P A,Max s {l * (s), k(l * (s))s1,..., S}arg max Σ r(k(l(s))) l(1),..., l(s) s1 s subject to Σ P l(s), k(l (s)) P A,Max (13) s1

10 Initialize: P (s)p l*(s),k(l*(s))+1 P l*(s),k(l*(s)) ; P (s)p l*(s),k(l*(s)) P l*(s),k(l*(s))-1 ; S r(k)r(k1)r(k); P l,k+1, P l,0 0, P r P A,Max Σ P l*(s),k(l*(s)) ; s1 While v arg max P (s); v arg min P (s); s s If( P (s)p r ) P r P r P (v ); k(l * (v )); Update P (v ), P (v ); elseig (( r(k(l * (v ))) r(k(l * (v ))1) & P (s)p r P (s)) or ( r(k(l * (v ))) r(k(l * (v ))1) & P (s) P (s))) P r P r P (v ) P (s); k(v );k(l * (v )); Update P (v ), P (v ), P (v ), P (v ); else break; endif; end while; P r

11 V [1] G. Song and Y. Li, ''Utility-based joint physical-mac layer optimization in OFDM,'' Proc. IEEE Glob. Commun. Confer. (Globecom), Vol. 1, Taipei, Taiwan, Nov. 2002, pp [2] S. Shakkottai, T.S. Rappaport, and P.C. Karlsson, ''Cross-layer design for wireless networks,'' IEEE Commun. Magazine, Vol. 41, October 2003, pp [3] J. Chuang and N.R. Sollenberger, "Advanced cellular internet service (ACIS)," IEEE Commun. Magazine, Vol. 36, Oct. 1998, pp [4] IEEE a, High-speed physical layer in the 5GHz band, [5] ETSI BRAN TS , Broadband radio access networks(bran) HIPERLAN type 2: physical(phy) layer, Apr [6] ETSI EN , Digital video broadcasting (DVB); framing, structure, channel coding and modulation for digital terrestrial television, Jun [7] IEEE ab-01/01r1, An Air Interface for Fixed Broadband Wireless Access Systems Part A: Systems between 2 and 11GHz, Jul [8] T. Keller and L. Hanzo, "Adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communications," Proc. IEEE, Vol. 88, May 2000, pp [9] R. Gru nheid, E. Bolinth, and H. Rohling, "A blockwise loading algorithm for the adaptive modulation technique in OFDM systems," Proc. IEEE Vehic. Techn. Confer. (VTC), Vol. 2, Atlantic City, NJ, U.S.A., Oct. 2001, pp [10] D. Kivanc, G. Li, and H. Liu, "Computationally efficient bandwidth allocation and power control for OFDMA," IEEE Trans. Wireless Commun., Vol. 2, Nov. 2003, pp [11] E. Bakhtiari and B.H. Khalaj, "A new joint power and subcarrier allocation scheme for multiuser OFDM systems," Proc. Pers. Indoor Mobile Radio Commun. (PIMRC), Vol. 2, Beijing, China, September 2003, pp [12] H. Yin and H. Liu, "An efficient multiuser loading algorithm for OFDM-based broadband wireless systems," Proc. IEEE Glob. Commun. Confer. (Globecom), Vol. 1, San Francisco, CA, U.S.A., Nov. 2000, pp [13] K.S. Kim, Y.H. Kim, and J.Y. Ahn, "Efficient adaptive transmission technique for LDPC coded OFDM cellular systems using multiple antennas," Electr. Letters, Vol. 40, Mar. 2004, pp

12 [14] T.J. Richardson and R.L. Urbanke, "The capacity of low-density parity-check codes under message-passing decoding," IEEE Trans. Inform. Theory, Vol. 47, Feb. 2001, pp

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¼º¿øÁø Ãâ·Â-1 Bandwidth Efficiency Analysis for Cooperative Transmission Methods of Downlink Signals using Distributed Antennas In this paper, the performance of cooperative transmission methods for downlink transmission