Parul Garg

Performance analysis of space-time coding with imperfect channel estimation

We analyze the error performance of a space-time coding system using N transmit and M receive antennas with imperfect channel estimation in flat Rayleigh fading. A least-squares estimate of the channel matrix is obtained by using a sequence of pilot code vectors. The estimate is found to be perturbed by an M/spl times/N perturbation matrix with zero-mean circular Gaussian entries. Using the characteristic function of the decision variable, we derive a closed-form expression for the pairwise error probability (PEP). From the same expression, the PEP in case of perfect channel estimation is also obtained. Numerical results show the degradation in performance due to imperfect channel estimation that can be compensated by increasing the number of receive antennas.

Outage and Error Rate Analysis of Network-Coded Coherent TWR-FSO Systems

This letter investigates a two-way relay assisted coherent free space optical system when the optical beam is subjected to gamma-gamma atmospheric turbulence and misalignment errors (pointing errors). A half-duplex relaying system consisting of two terminal nodes and a bidirectional relay is considered. The relay is based on decode-and-forward protocol and employs linear network coding to establish communication between the two terminal nodes in two time slots. Coherent detection with M-ary phase shift keying is employed. Closed form expressions for system outage and error performance for both binary and nonbinary cases are derived in terms of the well known Meijers G-function and are mathematically analyzed.

Performance analysis of full duplex decode-and-forward cooperative relaying over Nakagami-m fading channels

This paper analyses the error and outage performances of a dual hop, decode-and-forward cooperative system where the relay is equipped with full duplex relaying capabilities in a generalised fading environment. We evaluate the error performance in terms of average symbol error rate for M-ary phase shift keying and obtain the exact closed form expression for M=2. We also derive the exact closed form expression for outage probability considering flat, independent but not necessarily identical Nakagami-m fading channels for full duplex relaying. Copyright

Exact error performance of square orthogonal space- time block coding with channel estimation

Consider a wireless communication system in flat fading with N transmit and M receive antennas using space-time block coding, where N/spl times/1 code vectors are transmitted over L symbol intervals, resulting in an N/spl times/L code matrix. A least-squares estimate (LSE) as well as a minimum mean-square estimate (MMSE) of the M/spl times/N channel matrix is obtained from a sequence of pilot code vectors. For the case of linear square (i.e., with N=L) orthogonal codes over constant envelope constellations, we obtain an expression for the exact decoding error probability (DEP) for coherent maximum-likelihood decoding. We also find the coding gain for high average signal-to-noise ratio (SNR) per diversity branch in the case of Rayleigh fading. A comparison between both channel-estimation techniques is done in terms of the average pilot-power-to-signal-power ratio (APPSPR). It is found that MMSE requires lower pilot power than LSE for the same DEP and the same average SNR per diversity branch. In addition, the error performance with LSE approaches that with MMSE, with an increase of average SNR per branch or an increase of APPSPR.

Dual-Hop Optical Wireless Relaying Over Turbulence Channels With Pointing Error Impairments

In this paper, we present analytical expressions for the performance of dual-hop urban optical wireless communication system under the combined influence of atmospheric turbulence induced-fading and misalignment-fading (pointing errors). The system employs an amplify and forward relay with the assumption that channel state information is available at transmitting as well as receiving terminals. The atmospheric turbulence channels are modeled by independent but not necessarily identically distributed (i.n.i.d) Gamma-Gamma fading statistics with pointing error impairments. Using a tight upper bound for the end-to-end signal to noise ratio of the system, we derive the novel closed form expressions for the moment generating function and probability density function all in terms of Meijers G-function. Based on the aforementioned statistical results, accurate closed-form expressions for average symbol error rate for M-ary phase shift keying modulation schemes, outage probability and the ergodic capacity under four adaptive transmission policies namely optimal rate adaptation, optimal power and rate adaptation, channel inversion with fixed rate and truncated channel inversion with fixed rate are derived in terms of Meijers G -function function. Finally, the proposed mathematical analysis is accompanied with various numerical examples to demonstrate the effect of different system parameters on the system performance.

Outage analysis of full duplex decode and forward relaying over Nakagami-m channels

In this paper we analyze the outage behavior of a dual hop cooperative system where the relay is equipped with full duplex relaying (FDR) capabilities that means a relay can simultaneously receive and transmit unlike half duplex relaying (HDR), where the relay cannot receive and transmit simultaneously. We consider, in this analysis, that the reception at destination via any channel other than source-relay-destination is an interference. The interference between the receiving and transmitting antennas at the relay is also taken into account. At relay, the signal received from source is first decoded and then forwarded to destination.We derive the closed form expressions for outage probability considering flat, non-identical and independent Nakagami-m fading channels for both FDR and HDR. The comparison of outage performances reveals that FDR stands better than HDR for lower values of signal-to-noise ratio(SNR).

Analysis of subcarrier intensity modulation-based optical wireless DF relaying over turbulence channels with path loss and pointing error impairments

The authors consider a subcarrier intensity-modulated relayed optical wireless communication system under the combined influence of path loss, atmospheric turbulence and pointing error impairments. The turbulence-induced fading is modelled by independent but not necessarily identically distributed (i.n.i.d.) Gamma–Gamma fading statistics where the relaying protocol followed by the system is decode and forward (DF). First, the statistics of instantaneous signal-to-noise ratio at the destination is derived, followed by the novel and exact closed-form expression for outage probability of the system. Then using the moment generating function-based approach, the authors evaluate error performance of the system in terms of average symbol error rate (SER) for M-ary phase shift keying modulation schemes. Further, as a special case for M = 2, that is, binary phase shift keying modulation scheme, the exact closed-form expression of average SER is derived in terms of mathematically tractable Meijers G-function and extended generalised bivariate Meijers G-function. Finally, at the end of the paper, various numerical examples are included to demonstrate the effect of different system parameters on the performance of the system and are verified by Monte-Carlo simulations.

Bi-Directional Decode-XOR-Forward Relaying Over \(\mathcal {M}\) -Distributed Free Space Optical Links

In this letter, we consider the bi-directional cooperative communication where two users communicate to each other with the help of a relay. Considering the generalized M-distribution for the independent free space optical channels, the novel closed form expressions of the outage probability, and average symbol error rate are derived.

Relay Assisted Bi-directional Communication in Generalized Turbulence Fading

The bi-directional relaying has recently emerged as the spectrally efficient communication technique. In bi-directional relaying, two users exchange their information, with the help of a relay, in two time slots and, hence, achieve full-rate transmission. This paper considers a relay assisted bi-directional free-space optical communication system under the influence of generalized atmospheric turbulence fading and misalignment errors. The turbulence induced fading channels, which are independent but not necessarily identical, are modeled with M-distribution. In the presence of the misalignment fading characterized by the pointing errors, the new closed-form expressions for the outage probability and error rate are derived. The error performance of the considered system is analyzed for subcarrier intensity modulation-based M-ary phase-shift keying and M-ary quadrature-amplitude modulation constellations. The analytical results are validated through Monte Carlo simulations.

Ergodic Capacity of SIM-Based DF Relayed Optical Wireless Communication Systems

In this letter, we consider a dual-hop, subcarrier intensity modulation-based relayed optical wireless communication system under the combined influence of atmospheric turbulence and pointing error impairments. The turbulence-induced fading is modeled by independent but not necessarily identically distributed Gamma-Gamma fading statistics with misalignment fading. The relaying protocol followed by the relay is decode and forward. We first, derive the statistics of instantaneous signal-to-noise ratio at the destination, followed by the novel and exact analytical expressions for ergodic capacity of the system in terms of mathematically tractable Meijers G-function and extended generalized bivariate Meijers G-function.