We present a numerical analysis of the optimal number of active mobile users for minimizing average data delivery delay in intelligent people-centric urban sensing, in which context-aware mobile devices act as sensor-data carriers and sensor nodes act as data accumulators within CDMA cellular networks. In the analysis, we compute the optimal number of mobile users for different environmental conditions and then investigate the minimum average data delivery delay for this optimal number of mobile users.

For recent and future nanometer-technology VLSIs, static and dynamic delay variations become a serious problem. In many cases, the hold constraint, as well as the setup constraint, becomes critical for latching a correct signal under delay variations. This paper treats the hold constraint in a datapath circuit, and discusses a register assignment in high level synthesis considering delay variations. Our approach to ensure the hold constraint under delay variations is to enlarge the minimum-path delay between registers, which is called minimum-path delay compensation (MDC) in this paper. MDC can be done by inserting delay elements mainly in non-critical paths of a functional unit (FU). One of our contributions is to show that the minimization of the number of minimum-path delay compensated FUs is NP-hard in general, and it is in the class P if the number of FUs is a constant. A polynomial time algorithm for the latter is also shown in this paper. In addition, an integer linear programming (ILP) formulation is also presented. The proposed method generates a datapath having (1) robustness against delay variations, which is ensured partly by MDC technique and partly by SRV-based register assignment, and (2) the minimum possible numbers of MDCs and registers.

Under the conditions of Poisson arrivals and single copy transmission, we designed a minimum delay protocol for packet satellite communications. The approach is to assume a hybrid random-access/reservation protocol, derive its average delay and minimize the delay with respect to all tunable system parameters. We found that for minimum average delay,1) a spare reservation should normally but not always be made for each packet transmission.2) all unreserved slots (i.e. Aloha slots) should be filled with a packet rate of one per slot whenever possible. In other words, the utilization of Aloha slots should be maximized.3) an optimum balance between transmitting packets and making reservations before transmission should be maintained.