Roger L. Peterson

On collaborative detection of TV transmissions in support of dynamic spectrum sharing

The problem of collaborative spectrum sensing by a group of unlicensed devices is considered in this paper. The problem is placed in the specific setting of identifying available TV channels for use by the unlicensed devices. The system model and analysis developed in the paper is applicable to a number of more general dynamic spectrum sharing scenarios. Through analysis and simulations, it is shown in the paper that collaboration among nodes leads to more efficient spectrum utilization from a system-level point of view, while decreasing computational complexity of detection algorithms at the individual sensing nodes

Reliability-based type II hybrid ARQ schemes

Hybrid ARQ (HARQ) schemes use a combination of forward error correction and retransmissions to guarantee reliable packet data communications. In this work, we propose a HARQ scheme that exploits channel state information and received packet quality to improve system performance. Specifically, the receiver uses the average magnitude of the log-likelihood ratios corresponding to the received information bits, in order to determine the sizes of subsequent retransmissions. The proposed retransmission strategy attempts to maximize user throughput while satisfying a maximum packet delay constraint. The performance of our reliability-based type II HARQ (RBHARQ) scheme is evaluated in static and time-varying channels through simulations.

Reliability-based incremental redundancy with convolutional codes

Incremental redundancy, or Hybrid type-II ARQ (HARQ), algorithms use a combination of forward error correction and retransmissions to guarantee reliable packet data communications. In this work, we propose a HARQ algorithm that exploits received packet reliability to improve system performance. Specifically, the receiver uses the average magnitude of the log-likelihood ratios of the information bits as the packet reliability metric, which is then used to determine the sizes of subsequent retransmissions. The proposed retransmission strategy attempts to maximize user throughput while satisfying a maximum packet delay constraint. The performance of our reliability-based HARQ algorithm is evaluated in static and time-varying channels through simulations. Furthermore, analytical results on the relationship between the reliability metric, the code rate and the block error rate are presented.

On the Uplink Capacity of an 802.16j System

A multihop relay extension for IEEE 802.16e systems is the subject of ongoing standardization activities within the IEEE 802.16j Task Group. The emerging IEEE 802.16J standard enhances the 802.16e PHY and MAC to enable support of multihop routes between a mobile station and a base station through intermediate relay stations. Since it is believed that the capacity of a single-hop 802.16e system is uplink-limited, this paper evaluates potential capacity gains attained with the relay enhancement of the 802.16e uplink. The capacity here denotes either cumulative throughput for data traffic or total number of users for voice traffic supported, under certain system-specific constrains detailed below. We first develop a simplified one-dimensional model of a relay-enhanced 802.16e system and estimate the capacity gains via analysis and numerical optimization. Motivated by the capacity gains predicted by this first-order analysis, simulation results obtained from a full two-dimensional simulator modeling a realistic deployment of a relay-enhanced system are then presented. Based on the simulation results, a parametric analysis of relay deployment cost vs. the capacity gain is also presented.

System performance prediction for personal communication systems

A new location reliability formula, based on a path loss model appropriate for microcellular communication, is derived. Also an improved interpolation formula, for the calculation of log-normal shadow fading loss is presented.

Biorthogonal multicode modulation for high-rate high-reliability personal communications requiring controlled peak-to-average transmit power ratio

A modulation scheme is proposed for high-information-rate high-reliability personal communications where controlled peak-to-average transmit power ratio is an issue. The scheme is a hybrid of classical biorthogonal modulation and code division multiple access multicode modulation. Analytical and simulation results are presented for static AWGN channels and simulation results are presented for flat fading channels.

Multiple Dwell Serial Acquisition for Direct Sequence Spread Spectrum Systems

This paper provides a simple derivation of an expression for the mean synchronization time of a multiple-dwell serial search code synchronization scheme using non-coherent square law envelope detection. In addition, the results of a numerical optimization of the detector integration times and thresholds is presented for single, double, and triple dwell systems. The analysis applies to any search-lock strategy including those using both a different integration time and decision threshold on each dwell.