Aspects of the subject disclosure may include, for example, a repeater device having a first coupler to extract downstream channel signals from first guided electromagnetic waves bound to a transmission medium of a guided wave communication system. An amplifier amplifies the downstream channel signals to generate amplified downstream channel signals. A channel selection filter selects one or more of the amplified downstream channel signals to wirelessly transmit to the at least one client device via an antenna. A second coupler guides the amplified downstream channel signals to the transmission medium of the guided wave communication system to propagate as second guided electromagnetic waves. Other embodiments are disclosed.

Repeater and methods for use therewith

Aspects of the subject disclosure may include, for example, a client node device having a radio configured to wirelessly receive downstream channel signals from a communication network. An access point repeater (APR) launches the downstream channel signals on a guided wave communication system as guided electromagnetic waves that propagate along a transmission medium and to wirelessly transmit the downstream channel signals to at least one client device. Other embodiments are disclosed.

Client node device and methods for use therewith

Client node device with frequency conversion and methods for use therewith

We analyze the performance of amplify-and-forward dual-hop relaying systems in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, an exact analytical expression for and tight lower bounds on the outage probability are derived over independent, non-identically distributed Nakagami-m fading channels. Moreover, tractable upper and lower bounds on the ergodic capacity are presented at arbitrary signal-to-noise ratios (SNRs). Some special cases of practical interest (e.g., Rayleigh and Nakagami-0.5 fading) are also studied. An asymptotic analysis is performed in the high SNR regime, where we observe that IQI results in a ceiling effect on the signal-to-interference-plus-noise ratio (SINR), which depends only on the level of I/Q impairments, i.e., the joint image rejection ratio. Finally, the optimal I/Q amplitude and phase mismatch parameters are provided for maximizing the SINR ceiling, thus improving the system performance. An interesting observation is that, under a fixed total phase mismatch constraint, it is optimal to have the same level of transmitter (TX) and receiver (RX) phase mismatch at the relay node, while the optimal values for the TX and RX amplitude mismatch should be inversely proportional to each other.

I/Q Imbalance in AF Dual-Hop Relaying: Performance Analysis in Nakagami-m Fading

Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely impact the performance of orthogonal frequency division multiplexing (OFDM) systems, since they can result in inter carrier interference and rotation of the signal constellation. In this paper, we propose an expectation conditional maximization (ECM) based algorithm for joint estimation of channel, PHN, and CFO in OFDM systems. We present the signal model for the estimation problem and derive the hybrid Cramer-Rao lower bound (HCRB) for the joint estimation problem. Next, we propose an iterative receiver based on an extended Kalman filter for joint data detection and PHN tracking. Numerical results show that, compared to existing algorithms, the performance of the proposed ECM-based estimator is closer to the derived HCRB and outperforms the existing estimation algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the combined estimation algorithm and iterative receiver are more computationally efficient than existing algorithms and result in improved average uncoded and coded bit error rate (BER) performance.

Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detection, and Hybrid Cramér-Rao Lower Bound

A practical approach for detecting packet-based orthogonal-frequency-division multiplexing (OFDM) signals in the presence of phase noise is presented. An OFDM packet consists of several OFDM symbols with full-pilot symbols at the beginning followed by consecutive data symbols. Based on the full-pilot OFDM symbol, a frequency-domain joint phase noise and channel vector estimator is first derived. It is shown that the phase noise vector can be estimated by maximizing a constrained quadratic form without requiring knowledge of the channel vector. This estimated phase noise vector is then used to compute the least squares channel estimator. Assuming that the channel is constant during each packet, the estimated channel is used in subsequent data OFDM symbols for equalization and data detection. Since phase noise changes from one OFDM symbol to the next, the scattered pilots in each data OFDM symbol are used to non-iteratively estimate and mitigate the phase noise induced interference. A significant improvement in the signal-to-interference-plus-noise ratio is achieved using the proposed algorithm.

/pdf/a-non-iterative-technique-for-phase-noise-ici-mitigation-in-3fey00eze6.pdf

A Non-Iterative Technique for Phase Noise ICI Mitigation in Packet-Based OFDM Systems

We investigate the performance of orthogonal frequency division multiplexing (OFDM)-based dual-hop amplify-and-forward (AF) relay networks in the presence of phase noise (PHN). We show that the use of an AF relay may not be beneficial compared to a direct transmission in the presence of PHN. Using outage probability analysis, an upper bound on the allowable PHN level is derived which ensures that the dual-hop outperforms the direct transmission. To improve dual-hop transmission performance in the presence of PHN, we propose a reduced-complexity joint channel and PHN estimator using full-pilot OFDM symbols for AF relay transmission. The proposed approach achieves a lower mean squared error compared to the conventional channel estimator. In addition, we derive a joint data detection and PHN estimation scheme for comb-type data OFDM symbols by modifying the maximum ratio combining metric to account for the effect of PHN at the destination node.

/pdf/on-the-performance-of-ofdm-based-amplify-and-forward-relay-flfuauy0tw.pdf

On the Performance of OFDM-Based Amplify-and-Forward Relay Networks in the Presence of Phase Noise

The maximum likelihood estimate of the impulse response of a frequency-selective channel in the presence of phase noise and I/Q imbalance is derived. The complexity of the joint estimator is reduced using approximate cost functions for both phase noise and I/Q imbalance. The proposed estimator is first applied to OFDM transmission in a single-input single-output system and then generalized to multi-input multi-output OFDM systems. The bit error rate performance of popular space-time codes for two and four transmit antennas is evaluated under zero-forcing, minimum mean squared error and maximum likelihood detection rules. An expression for the residual inter-carrier interference variance after phase noise and I/Q imbalance compensation is derived and compared to the uncompensated case. Significant improvement in signal-to-interference-noise is obtained with the proposed algorithm.

/pdf/reduced-complexity-joint-baseband-compensation-of-phase-1kc6reglyu.pdf

Reduced-Complexity Joint Baseband Compensation of Phase Noise and I/Q Imbalance for MIMO-OFDM Systems

We propose a new full-rate space-time block code (STBC) for two transmit antennas which can be designed to achieve maximum diversity or maximum capacity while enjoying optimized coding gain and reduced-complexity maximum-likelihood (ML) decoding. The maximum transmit diversity (MTD) construction provides a diversity order of 2Nr for any number of receive antennas Nr at the cost of channel capacity loss. The maximum channel capacity (MCC) construction preserves the mutual information between the transmit and the received vectors while sacrificing diversity. The system designer can switch between the two constructions through a simple parameter change based on the operating signal-to-noise ratio (SNR), signal constellation size and number of receive antennas. Thanks to their special algebraic structure, both constructions enjoy low-complexity ML decoding proportional to the square of the signal constellation size making them attractive alternatives to existing full-diversity full-rate STBCs in [6], [3] which have high ML decoding complexity proportional to the fourth order of the signal constellation size. Furthermore, we design a differential transmission scheme for our proposed STBC, derive the exact ML differential decoding rule, and compare its performance with competitive schemes. Finally, we investigate transceiver design and performance of our proposed STBC in spatial multiple-access scenarios and over frequency-selective channels.

/pdf/new-rate-2-stbc-design-for-2-tx-with-reduced-complexity-53uyxgnqth.pdf

New rate-2 STBC design for 2 TX with reduced-complexity maximum likelihood decoding

A new information lossless, full-rate space-time block code is presented for 2 transmit antennas over 2 symbol periods. We show that our code is capacity-achieving and exploit its special algebraic structure to derive a reduced-complexity maximum-likelihood (ML) decoding algorithm. When the number of receive antennas is greater than 1, our code outperforms the Alamouti code. Comparing the performance of our code with state-of-the-art B2Phi and Golden codes in [4] and [7], demonstrates competitive performance for practical low-to-medium SNR ranges, for high spectral efficiencies, and as the number of receive antennas increases while requiring much lower ML decoding complexity.

P. Rabiei

Papers

A Non-Iterative Technique for Phase Noise ICI Mitigation in Packet-Based OFDM Systems

On the Performance of OFDM-Based Amplify-and-Forward Relay Networks in the Presence of Phase Noise

Reduced-Complexity Joint Baseband Compensation of Phase Noise and I/Q Imbalance for MIMO-OFDM Systems

New rate-2 STBC design for 2 TX with reduced-complexity maximum likelihood decoding

A New Information Lossless STBC for 2 Transmit Antennas with Reduced-Complexity ML Decoding