Analysis of Controlled Probabilistic Access with Multipacket Reception

Abstract

Multipacket reception (MPR) capability provides the opportunity to improve bandwidth utilization while reducing complexity of the medium access control layer. Specifically, it has been shown that ALOHA random access tends to become asymptotically optimal as the receiver's joint decoding capability of the receiver grows to infinity. However, the average traffic offered to the medium is required to remain below a threshold in order for the MPR capability to be utilized efficiently.The effect of controlling the access probability according to the instantaneous offered traffic is studied in this paper. It is shown that, as the average rate of the offered traffic exceeds the optimal value, a dynamic control strategy can increase the maximum expected throughput of probabilistic access dramatically compared to uncontrolled ALOHA. The average throughput achieved by this strategy is analyzed and a lower bound on the system throughput of genie-aided probabilistic access is derived. Finally, the effect of uncertainty about the offered traffic is addressed and an approximation for the resulting performance loss is presented.

Multi-code wireless packet random access

“…Fig. 8 also shows the lower bound derived in [27] for the simplified model (7). Without this, or an equivalent, MAC functionality MPR traffic could quickly collapse, since uncontrolled, the system is always unstable under the MPR model (7).…”

Controlled random access with multipacket reception and traffic uncertainty

“…For simplicity of analysis, we assume slotted communications at the MAC level. The MPR model used in this paper is described by [4], [5] …”

“…Since the performance of this scheme depends strongly on the accuracy of the traffic estimates, the effect of traffic uncertainty and estimation errors was briefly discussed in [5]. In this paper, we address this issue more extensively.…”

“…It can be seen that increasing K improves the bandwidth efficiency while also increasing the negative slope of the system throughput for traffic exceeding the optimal value. Therefore, it was proposed in [4], [5] to adaptively adjust the access probability according to the instantaneous traffic. In the rest of this paper, the term "controlled random access" is used for a random access scheme where each node controls its transmission by setting a transmission probability as a function of its local knowledge of the current traffic statistics.…”

“…Controlled random access was examined in [4] and analyzed in [5] for the case where each node can acquire perfect knowledge of the number of active nodes in its vicinity. Since the performance of this scheme depends strongly on the accuracy of the traffic estimates, the effect of traffic uncertainty and estimation errors was briefly discussed in [5].…”