Design of a Practical and Compact mm-Wave MIMO System with Optimized Capacity and Phased Arrays

In this paper we evaluate the feasibility of short range outdoor mm-wave MIMO links in the 70 GHz portion of the E-band (71–76 GHz). We use phased arrays in order to strongly reduce the impact of the multipath components, thus making the channel mainly line-of-sight (LOS). We design the array using a simple patch as a single element and simulate the performances for a 200 m link and a MIMO system with equal element spacing at the transmitter and the receiver. Each node of the MIMO system consists of a uniform rectangular array (URA) where the single element is a patch antenna, in order to achieve higher gains and narrow beams. Such configuration is much more compact compared to the antennas currently employed for the same bandwidth. We optimize the interelement distances at the transmitter and the receiver and evaluate the capacity achievable with different array sizes. The results show that, for the proposed link budget, capacity up to 29 bit/s/Hz is achievable at a range of 200 m, with practical dimensions. We also show that the beamforming capabilities make the design much more flexible than the single reflector antenna systems. In the last part of the paper, we verify that our antenna can also operate in rainy conditions and longer ranges

Design of capacity-optimal high-rank line-of-sight MIMO channels

This paper describes a technique for realizing a high-rank channel matrix in a line-of-sight (LOS) multiple-input multiple-output (MIMO) transmission scenario. This is beneficial for systems which are unable to make use of the originally derived MIMO gain given by independent and identically distributed (i.i.d.) flat Rayleigh fading channels. Typical applications are fixed wireless access (FWA) and radio relay systems. The technique is based on optimization of antenna placement in uniform linear arrays with respect to mutual information (MI) for pure LOS channels. Both the case where the channel is only known at the receiver and the case where the channel is known at the transmitter and receiver are treated. By introducing a new and more general 3-D geometrical model than that applied in earlier works, additional insight into the optimal design parameters is gained. We also perform a novel analysis of the sensitivity of the optimal design parameters, and derive analytical expressions for the eigenvalues in the pure LOS channel case, which are valid also when allowing for non-optimal design. Furthermore, we investigate the approximations introduced in the derivations, in order to reveal when the results are applicable, which turns out to be for most practical situations. The LOS transmission matrix is used in a Ricean fading channel model which incorporates spatial correlation between the non-LOS components, and performance is evaluated with respect to the average MI and the MI cumulative distribution function. Our results show that even with some deviation from the optimal design, the LOS MIMO scenario outperforms the i.i.d. Rayleigh scenario in terms of MI

Rate and power allocation for discrete-rate link adaptation

Link adaptation, in particular adaptive coded modulation (ACM), is a promising tool for bandwidth-efficient transmission in a fading environment. The main motivation behind employing ACM schemes is to improve the spectral efficiency of wireless communication systems. In this paper, using a finite number of capacity achieving component codes, we propose new transmission schemes employing constant power transmission, as well as discrete- and continuous-power adaptation, for slowly varying flat-fading channels. We show that the proposed transmission schemes can achieve throughputs close to the Shannon limits of flat-fading channels using only a small number of codes. Specifically, using a fully discrete scheme with just four codes, each associated with four power levels, we achieve a spectral efficiency within 1 dB of the continuous-rate continuous-power Shannon capacity. Furthermore, when restricted to a fixed number of codes, the introduction of power adaptation has significant gains with respect to average spectral efficiency and probability of no transmission compared to a constant power scheme.publishedVersio

Sequential Decoding of Tailbiting Convolutional Codes for Hybrid ARQ on Wireless Channels

Sequential decoding of long constraint length convolutional codes is proposed for hybrid automatic repeat request packet data transmission on a Rayleigh fading channel. In this scheme computational complexity (the timeout condition) is applied for error detection. In order to improve the throughput, tailbiting codes are used. Furthermore, a method for estimating the initial state of the encoder is described, and for most packet lengths the tailbiting scheme with initial state/tail estimation yields significantly improved throughput compared to the case with a known tail. A throughput of 0.90 at a signal to noise ratio per coded bit of 15 dB shows this coding scheme to be competitive for wireless packet data services. Although interleaving must be performed over one packet only, high throughput is maintained also for correlated fading. Keywords--- Sequential decoding, packet data, automatic repeat request (ARQ), tailbiting, systematic encoder, Fano algorithm, Rayleigh fading, wireless ..

Sequential Decoding of Tailbiting Convolutional Codes for Packet Data on Rayleigh Fading Channels

Sequential decoding of long constraint length convolutional codes is proposed for hybrid automatic repeat request packet data transmission on a Rayleigh fading channel, and computational complexity (the timeout condition) is applied for error detection. In order to improve the throughput, tailbiting codes are used. Furthermore, a method for estimating the initial state of the encoder is described, and for most packet lengths this scheme yields negligible loss compared to the case with a known tail. Although interleaving must be performed over one packet only, high throughput is maintained also for correlated fading. A throughput of 0.90 at a signal to noise ratio per coded bit of 15 dB shows this coding scheme to be competitive for wireless packet data services. Keywords--- Sequential decoding, packet data, automatic repeat request (ARQ), tailbiting, Fano algorithm, Rayleigh fading, wireless communication. I. Introduction U P to now wireless communication systems have been designed..

Coding, Decoding and Multiuser Detection for Wireless Communications

In the strive for making the Universal Mobile Telecommunication System (UMTS) a reality, concepts and techniques are to be developed which can provide both high system capacity and sufficient quality for the increasing number of mobile users. To obtain these objectives, powerful and flexible error control coding is needed, as well as efficient means for many users to share the same communication medium. This thesis contributes by presenting new optimum convolutional channel codes, outperforming those previously reported. These new and improved codes are then used as a basis for deriving flexible and powerful families of codes with many code rates. The various wireless services require different levels of error protection as well as a means for matching different data rates to the rate of the channel. Rate matching in multirate direct-sequence codedivision multiple-access (DS-CDMA) systems is described and the performance is evaluated in terms of efficiency. Furthermore an error control..

Evaluation of Coded CDMA with Interference Cancellation

The performance of an asynchronous CDMA system (up-link) employing very low-rate maximum free distance codes for combined coding and spreading is analyzed when successive or parallel interference cancellation is applied. An analytical approach to the evaluation of the bit error rate is presented and shown to give results close to simulations. Our results show that the code-spread system outperforms the conventionally coded and spread system. Without interference cancellation the single-user bound is never reached (except for one user). With two stages of parallel interference cancellation, a code-spread system with a load only slightly less than 1 bit/chip can obtain a bit error rate very close to that of a single-user system. Keywords--- CDMA, low-rate convolutional codes, orthogonal codes, successive interference cancellation, parallel interference cancellation, rate-compatible, maximum free distance. I. Introduction D IRECT-sequence code-division multiple-access (DSCDMA) is the ..

Code-Spread CDMA using Low-Rate Convolutional Codes

In CDMA systems maximum theoretical performance can be obtained by spreading with low-rate error control codes. Previously, orthogonal and superorthogonal codes have been proposed for this purpose. We present in this paper a family of rate-compatible lowrate convolutional codes with maximum free distance. The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and superorthogonal codes as well as conventional coding/spreading schemes. We also show that our low-rate codes will give simple encoder and decoder implementation. With these codes any 1=n rate can be obtained regardless of the constraint length, resulting in a more flexible and powerful scheme than those proposed up to now. Keywords--- CDMA, low-rate convolutional codes, orthogonal codes, superorthogonal codes, rate-compatible, maximum free distance. I. Introduction S PREAD spectrum systems have been used for decades as a way of achieving robustness agai..