IEEE COMMUNICATIONS LETTERS, VOL. 12, NO. 4, APRIL 2008 225 Information-Guided Channel-Hopping for High Data Rate Wireless Communication Yuli Yang and Bingli Jiao Abstract— In this letter, we introduce information-guided channel-hopping, a new scheme for high data rate communi- cation over Rayleigh fading channel using multiple transmit antennas. This scheme is proposed based on the fact that the inde- pendence character of multi-channel can be used as an additional information transmitting channel, and the maximum likelihood decoding can be achieved in a simple way by decoupling of the signals conveyed by different methods. The analysis results prove that the capacity behavior of this scheme is better than that of the space-time block coding for more than two transmit antennas. Index Terms— Capacity, multi-antenna system, information- guided channel-hopping (IGCH), space-time block coding (STBC). I. I NTRODUCTION I N [1] and [2], space-time block coding (STBC) is proposed as a remarkable transmission scheme for the multi-antenna system. It has an elegant mathematical solution for providing full diversity over the coherent, flat-fading channels. However, when the number of transmit antennas is more than two, STBC incurs a loss in capacity[2][3], that is, its capacity is smaller than the true channel capacity computed by [4] and [5]. The main reason behind this is that the equivalent code rate of STBC can not achieve the maximum possible transmission rate for more than two transmit antennas. In addressing the issue of high code rate, we proposed a new transmission method for multi-antenna system, which allows additional information is conveyed by the selection among multiple independent channels and accordingly is named Information-Guided Channel-Hopping (IGCH) scheme. In the following sections, we will describe this transmission scheme and its corresponding decoding algorithm in detail. The anal- ysis results of the capacity behavior will show that IGCH can be an alternative scheme in the multi-antenna systems with more than two transmit antennas. II. I NFORMATION-GUIDED CHANNEL-HOPPING SYSTEM Consider an M × 1 system, i.e., a system with M transmit- and 1 receive- antennas. Let h m (m =1, 2, ··· ,M ) be the flat- fading channel coefficient from the mth transmit antenna to the receiver. We always assume that the channel state information is not known at the transmitter but completely known at the receiver, and that all flat-fading channels in the system satisfy Manuscript received November 25, 2007. The associate editor coordinating the review of this letter and approving it for publication was P. Demestichas. Y. Yang is with the Research & Innovation Center, Alcatel-Lucent Inc., Shanghai 201206, China. She was with the Department of Electronics, Peking University, Beijing 100871, China (e-mail: yang yuli@hotmail.com). B. Jiao is with the Department of Electronics, Peking University, Beijing 100871, China (e-mail: jiaobl@pku.edu.cn). Digital Object Identifier 10.1109/LCOMM.2008.071986. the independent and identical complex Gaussian distribution [3][4]. A. Transmission scheme At the transmitter, the IGCH scheme prescribes the simul- taneous transmission of two data streams: one is mapped onto the index of the transmit antenna selected for transmission (i.e., in a system with M transmit antennas, log 2 M bits can be used to choose which transmit antenna is transmitting at each time slot), whereas the other stream is encoded conventionally and radiated by the selected transmit antenna. We name the former channel symbol and the latter radiated symbol, expressed by x and x ch , respectively, where x ch ∈ {♯h 1 , ♯h 2 , ··· , ♯h M } with ♯h m (m =1, 2, ··· ,M ) for the index of the mth channel. If x ch = ♯h m , x will be transmitted over the mth channel, and therefore, the received signal will be expressed by y = h m x + n m , (1) where x ∈{s 1 ,s 2 , ··· ,s N } is the radiated symbol corre- sponding to an N -point modulation constellation with symbol power of σ 2 X , and n m is the received additive white complex Gaussian noise with zero-mean and variance of σ 2 N . B. The decoding algorithm In the IGCH system, the task of decoding is to find not only the radiated symbol but also the channel symbol mapped by the selection of channel. Naturally, the maximum likelihood (ML) decoding algorithm can be used to estimate the radiated symbol and channel symbol simultaneously as following: choose ˆ x = s n and ˆ x ch = ♯h m if and only if d 2 (y,h m s n ) ≤ d 2 (y,h m ′ s n ′ ) , ∀m = m ′ ,n = n ′ , (2) where d 2 (u, v) is the squared Euclidean distance between signals u and v. However, when the number of transmit antennas is fixed, the computational complexity of this de- coding algorithm (measured by the number of multiplication operations) increases exponentially with the number of bits mapped onto the modulation constellation of the radiated symbol, i.e., the number of multiplication operations in the decoding is NM . In order to reduce the computational complexity, the decod- ing of IGCH scheme will be divided into two steps: firstly, the candidate decisions are made in terms of ˆ x m = arg min s∈{s1,s2,··· ,sN} d 2  s, h ∗ m y |h m | 2  ,m =1, 2, ··· ,M, (3) 1089-7798/08$25.00 c  2008 IEEE