In this letter, we investigate tight analytical and asymptotic upper bounds for bit error rate (BER) of constitutional codes over exponentially correlated Nakagami-m fading channels. Specifically, we derive the BER expression depending on an exact closed-form formula for pairwise error event probabilities (PEEP). Moreover, the corresponding asymptotic analysis in high signal-to-noise ratio (SNR) regime is also explored, which is verified via numerical results. This allows us to have explicit insights on the achievable coding gain and diversity order.

In this paper, we investigate a cooperative communication system comprised of a source, a destination, and multiple decode-and-forward (DF) relays in the presence of a potential malicious eavesdropper is within or without the coverage area of the source. Based on the more general Nakagami-m fading channels, we analyze the security performance of the single-relay selection and multi-relay selection schemes for protecting the source against eavesdropping. In the single-relay selection scheme, only the best relay is chosen to assist in the source transmission. Differing from the single-relay selection, multi-relay selection scheme allows multiple relays to forward the source to the destination. We also consider the classic direct transmission as a benchmark scheme to compare with the two relay selection schemes. We derive the exact closed-form expressions of outage probability (OP) and intercept probability (IP) for the direct transmission, the single-relay selection as well as the multi-relay selection scheme over Nakagami-m fading channel when the eavesdropper is within and without the coverage area of the source. Moreover, the security-reliability tradeoff (SRT) of these three schemes are also analyzed. It is verified that the SRT of the multi-relay selection consistently outperforms the single-relay selection, which of both the single-relay and multi-relay selection schemes outperform the direct transmission when the number of relays is large, no matter the eavesdropper is within or without the coverage of the source. In addition, as the number of DF relays increases, the SRT of relay selection schemes improve notably. However, the SRT of both two relay selection approaches become worse when the eavesdropper is within the coverage area of the source.

In this paper, we derive two simple asymptotic closed-form formulas for the average bit error probability (BEP) of differential quaternary phase shift keying (DQPSK) with Gray encoding and a simple asymptotic approximation for the average symbol error probability (SEP) of doubly-differential quaternary phase shift keying (DDQPSK) in Nakagami-m fading channels. Compared with the existing BEP/SEP expressions, the derived concise formulas are much more effective in evaluating the asymptotic properties of DQPSK/DDQPSK with various Nakagami fading parameters, the accuracy of which is verified by extensive numerical results.

Cooperative relay selection, in which one of multiple relays is selected to retransmit the source signal to the destination, has received considerable attention in recent years, because it is a simple way to obtain cooperative diversity in wireless networks. The exact expression of outage probability for a decode-and-forward cooperative relay selection with multiple source and destination antennas over Rayleigh fading channels was recently derived in [9]. In this letter, we derive the exact expressions of outage probability and diversity-multiplexing tradeoff over independent and non-identically distributed Nakagami-m fading channels as an extension of [9]. We then analyze the effects of various parameters such as fading conditions, number of relays, and number of source and destination antennas on the outage probability.

In this paper, we consider a dual-hop wireless cooperative network with amplify-and-forward (AF) relaying. The output signal-to-noise ratio (SNR) at the destination of the AF cooperative networks is in the form of the sum of harmonic mean of the source-relay channel SNR and the relay-destination channel SNR. Instead of deriving the exact probability density function (PDF) of the output SNR, we study the series expansion of this PDF around zero. This result is then applied to evaluate the performance of the AF cooperative systems over Nakagami-m fading channels, and closed-form high-SNR approximations of the average symbol error rate (SER) and the outage probability are derived. Next, we investigate the optimal power allocation (OPA) among the source node and the relays to minimize the approximate SER as well as the outage probability. It is shown that the optimal power allocation depends on the channel m parameters and the ratio of the source-relay channel gain to the relay-destination gain. In addition to the optimal power allocation, we also propose a low complexity sub-optimal power allocation (SubOPA) scheme. The performance improvement with optimal and sub-optimal power allocation is analyzed and validated by numeric results. It is shown that equal power allocation is near optimal when the relays are close to the source, while significant performance improvement is observed by both the optimal and sub-optimal power allocation schemes when the relays are close to the destination.

This letter studies the asymptotic bit error rate (BER) performance of multihop communication systems with amplify-and-forward relaying over Nakagami-m fading channels. Since it is difficult to find the exact probability density function (PDF) of the output signal-to-noise ratio (SNR) at the destination, we resort to the series expansion of this PDF in the neighborhood of zero. Building upon this result, a closed-form expression for the average BER in the high SNR region is derived. Numeric results show that the derived asymptotic BER expression is accurate at medium and high SNR for both independent identically distributed (i.i.d.) and independent non-identically distributed (i.n.i.d.) channels.

In this letter, new results on the BER performance of multitone DS-CDMA systems for transmissions over Nakagami-m fading channels with exponentially decaying multipath intensity profile are presented. The results show that, in viewpoint of the BER performance, there is a critical relation between the number of resolvable paths and the effect of the rate of average power decay.

A convenient signaling scheme, termed orthogonal on-off BPSK (O3BPSK), along with a simple one-shot linear decorrelating detector (LDD) has been proposed by Zheng and Barton as a technique for near-far resistant detection in the asynchronous DS/CDMA systems. The temporally adjacent bits from different users in the received signals are decoupled by using the on-off signaling, and the data rate is maintained with no increase in transmission rate by adopting an orthogonal structure. The system performance of this signaling scheme in terms of bit error rate (BER) has been analyzed over an AWGN channel by Zheng and Barton. In this paper, we further study the system performance over Nakagami-m fading channel. A closed form for the BER of such a scheme is successfully derived. Numerical results show that the O3BPSK signal scheme along with the LDD receiver still offers a good near-far resistant property over Nakagami-m channel.