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Many future wireless sensor networks will feature very high node density and low data rates per node as well as the desire for low latency and high network dependability. Existing medium access control (MAC) layer protocols, namely IEEE 802.15.4, may not be suitable for these networks due to their reliance on carrier sense multiple access with collision avoidance (CSMA-CA) contention processing. A modified IEEE 802.15.4 MAC protocol that supports a receiver-assigned code division multiple access (RA-CDMA) contention mechanism is modeled in this paper, and is shown to enable higher network scalability while improving network performance and contributing additional robustness against interferers. This paper focuses on a comparison of the contention mechanisms and the network scalability of IEEE 802.15.4 nonbeacon enabled mode and RA-CDMA, along with a MATLAB simulation framework used for end-to-end simulations of the protocols. Simulations suggest that IEEE 802.15.4 networks begin to break down in terms of throughput, latency, and delivery ratio at a relatively small overall network size compared to RA-CDMA networks. Results show that networks using the proposed RA-CDMA multiple access can support node densities approximately two to three times higher than IEEE 802.15.4 with minimal changes to the IEEE 802.15.4 MAC, in addition to lower latencies and improved interference mitigation.

Test and evaluation (T&E) is a critically important step before in-the-field deployment of radio frequency hardware in order to assure that the hardware meets its design requirements and specifications. Typically, T&E is performed either in a lab setting utilizing a software simulation environment or through real-world field testing. While the former approach is typically limited by the accuracy of the simulation models (of the anticipated hardware effects, channel conditions, etc.) and by non-real-time data rates, the latter can be extremely costly in terms of time, money, and manpower. To address these issues, this work presents the development of an FPGA-based T&E tool that allows for real-time pseudo-random signal generation for testing radio frequency receiver hardware (such as communication receivers, spectrum sensors, etc.). In particular, a framework is developed for an FPGA-based implementation of a test signal emulator that allows for user-defined randomization of test signal parameters such as center frequencies, bandwidths, start times, and durations, as well as receiver and channel effects such as additive white Gaussian noise (AWGN). To test the accuracy of the developed emulation framework, the randomization properties of the framework are analyzed to assure correct probability distributions and independence. Additionally, FPGA implementation decisions such as bit precision vs. accuracy of the generated signal and the impact on the FPGA’s hardware footprint are analyzed. Ultimately, it is shown that this framework is easily extensible to other signal types and channel models.