In recent years, the world has witnessed the deployment of several 3G and 3.5G wireless networks based on technologies such as CDMA 1x EVolution Data-Only (EVDO), High-Speed Downlink Packet Access (HSDPA), and mobile WiMax (e.g., WiBro). Although 3G and 3.5G wireless networks support enough bandwidth for typical Internet applications, their performance varies greatly due to the wireless link characteristics.We present a measurement analysis of the performance of UDP and TCP over 3G and 3.5G wireless networks. The novelty of our measurement experiments lies in that we took our measurements in a fast moving car on a highway and in a high-speed train running at 300 km/h. Our results show that mobile nodes experience far worse performance than stationary nodes over the same network.

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This paper presents an automatic modulation and coding scheme (MCS) level adaptation algorithm to embrace Internet of Things (IoT) devices by improving the area spectral efficiency of carrier-sense multiple access with collision avoidance (CSMA/CA) wireless networks. In the proposed algorithm, senders of CSMA/CA wireless networks use the signal to interference plus noise ratio of acknowledgment frames from their receivers to estimate channel statuses between the senders and the receivers. Using the estimated channel status of each receiver, senders control sending rates of traffic by adjusting MCS levels of packets destined for each receiver. We use Poisson point processes (PPPs) to model the locations of participating nodes (i.e., access points and wireless devices) in a given area. We evaluate the effectiveness of the proposed algorithm using an event-driven ns-2 simulator for various PPP densities of access points and wireless devices.

WiBro (Wireless Broadband Internet), the Korean version of mobile WiMAX compatible standard, provides high-speed mobile data service. Although mobile WiMAX services are being deployed, there exist few reports about WiBro performance. In this work, we measure and analyze best-case performance of WiBro. In order to measure one-way delay, we develop a GPS synchronization device to measure one-way delay.Our measurement shows that the maximum throughput over the WiBro network is 10 Mbps in downlink and 2.5 Mbps in uplink. We estimate that both the base station and WiBro modems have large buffers up to 2 s and 500 ms and minimum one-way delay of 76 ms and 11 ms for uplink and downlink, respectively. We measure TCP throughput over WiBro by varying the send buffer and receive buffer sizes. To fully exploit the high bandwidth of Wibro, we conclude the TCP needs along with the minimum of 128 KB buffer size.

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