We consider a single-branch, mobile multihop relaying (MMR) network with limited channel state information (CSI) at the destination. The considered CSI signalling strategy reduces the signalling overhead at each relay by at least 50%. We show that this significant overhead reduction comes at the expense of no performance loss at all when hard maximum likelihood detection is carried out at the destination. Furthermore, we consider the use of the MMR system with concatenated channel codes to carry out soft maximum a posteriori (MAP) detection, and demonstrate that with channel codes employed the optimum detection rule becomes prohibitively complex to implement. We propose two approximate soft MAP detection schemes to make the detection feasible for the system, and demonstrate that the performance is either almost identical to or slightly degraded from the ideal case with full CSI at the destination.

We derive estimates of mean time to failure and mean time to recover/repair for both hardware and software in a large wireless telecommunications system, based on six months of manually recorded outage data. The observed failure and recovery distributions are not consistent with simple exponential processes. The data can be described by Weibull or two-stage hyper-exponential distributed processes. The duration distributions for scheduled and unscheduled software outages have very different characteristics. The complex distributions observed may be the composition of simple independent processes which cannot be separated in this data set due to a lack of adequately detailed information or proper characterization of outage causes. In this system we found a coverage of /spl sim/98% for autorecovery from unscheduled software failures with an autorepair fraction of /spl sim/36%.

This paper presents empirical results on the performance of CD, a compiler directed memory management policy, and the Working Set policy in a multiprogramming system. A description of the multiprogramming model used in the experiments is also presented. The results show that CD outperforms WS in terms of fault rate, space time cost, and throughput characteristics. Moreover, WS is shown to lack controllability. Two anomaly types are reported in this paper, both of which are exhibited by WS but not by CD.

A Compiler Directed Memory Management Policy for numerical programs is described in this paper.The high level source codes of numerical programs contain useful information which can be used by a compiler to determine the memory requirements of a program.Using this information, the compiler can insert some directives into the operating system for effective management of the memory hierarchy.During the program's execution the operating system dynamically allocates to a program the space it requires as specified by the received directive.The new policy is compared with LRU and WS policies.Empirical results presented in this paper sliow that the CD policy can out-perform LRU and WS by a wide margin.