This paper jointly optimizes the zoning, scheduling, and pricing of a zonal-based flexible bus service (ZBFBS). ZBFBS categorizes and groups the origin-destination (OD) pairs of ride requests by geographical zones to provide door-to-door transit services while considering dynamic stochastic elastic demand volume, stochastic ride request locations, and time window constraints. The integrated problem can be formulated in two ways, either by designing the bus service routing in response to the realized demand, referred to as the demand-responsive method, or by a stochastic programming approach that accounts for the demand distribution. The former first clusters the realized requests into zones through the k-means algorithm, and then solves the joint vehicle scheduling and passenger assignment problem. As for the latter, a bi-level framework is proposed: the upper level optimizes the zoning, and the lower level maximizes the profit by scheduling and pricing the ZBFBS service. For this purpose, hexagonal and rectangular zonings are considered, whose positions and dimensions are optimized by a line search algorithm, with a deterministic approximation approach to significantly reduce the solution time. This framework is applied to a scenario based on actual ride-hailing data in Chengdu, China. The results demonstrate the benefit of the bi-level framework in producing an optimal zonal design. Also, the proposed bi-level stochastic zonal design framework outperforms the demand-responsive method in a tight planning time.

Current sensor network nodes are not designed for a rapid succession of large-scale deployments. While hundreds of nodes have been deployed in static networks (e.g. ExScale, GreenOrb) large-scale, mobile, repetitive deployments are difficult to manage. We developed a new platform, the WREN, to be a low-cost, easy to maintain and rapid to deploy, wireless sensing node for human contact network measurements.

Intelligent mobile terminals (or users) of next generation wireless networks are expected to initiate voice over IP (VoIP) calls using session set-up protocols like H.323 or SIP (session initiation protocol). To guarantee the service quality of such applications, the call set-up protocol should be robust against network impairments. We analyze the performance of the H.323 call set-up procedure over wireless links using a simple call model under two modes of operations, namely, regular and fast connect. The proposed model assumes the presence of a radio link protocol (RLP) and recommends that the VoIP packets be transferred without any RLP retransmissions, while H.323 control packets be transferred with RLP retransmissions. Our analytical models and detailed experiments show that the VoIP call set-up performance can undergo significant degradation if RLP is not used at all, even for moderately high frame error rates (FERs) in wireless links. On the other hand, a robust radio link layer, such as RLP, can improve the call-set-up delay performance as compared to the existing wireless voice call-set-up delay.