No abstract

Nowadays, wireless communication technology is developing rapidly. However, this technology still has some weaknesses, e.g. large bandwidth requirement and multipath fading. To overcome these weaknesses, MIMO OFDM technique is needed. This paper implements MIMO OFDM 2x2 communication system in Universal Software Radio Peripheral (USRP). The performance of MIMO OFDM 2x2 is shown by the throughput value. This value is compared to the throughput value of single carrier and SISO OFDM. The modulations used are BPSK, 4-QAM, and 16-QAM. In 4-QAM modulation, the throughput value of MIMO OFDM is significantly larger than throughput value of single carrier and SISO OFDM. The throughput value of single carrier communication system is 27.71 Mbit/s, while the throughput value of the SISO OFDM communication system is 60.27 Mbit/s, and the throughput value of the MIMO OFDM 2x2 communication system is 123.03 Mbit/s. Intisari-Dewasa ini teknologi komunikasi nirkabel berkembang dengan cepat. Meskipun demikian, teknologi ini masih memiliki beberapa kekurangan, yakni kebutuhan lebar pita yang besar dan adanya multipath fading. Untuk mengatasi hal tersebut, diperlukan adanya teknik MIMO OFDM. Makalah ini mengimplementasikan sistem komunikasi MIMO OFDM 2x2 pada Universal Software Radio Peripheral (USRP). Kinerja dari sistem komunikasi MIMO OFDM 2x2 ini dilihat dari nilai throughput. Nilai throughput tersebut dibandingkan dengan nilai throughput pada single carrier dan SISO OFDM. Modulasi yang digunakan ialah BPSK, 4-QAM, dan 16-QAM. Pada modulasi 4-QAM, throughput MIMO mengalami kenaikan yang signifikan dibandingkan single carrier dan SISO OFDM. Nilai throughput yang dihasilkan pada sistem komunikasi single carrier sebesar 27,74 Mbit/s, sedangkan nilai throughput pada SISO OFDM sebesar 60,27 Mbit/s, dan throughput pada MIMO OFDM 2x2 adalah sebesar 123,03 Mbit/s.

Currently, the IEEE 802.11 wireless local-area network (WLAN) has been prevalent around the world due to the advantages of mobility, flexibility, and scalability. WLAN offers the wireless internet-access method through an access-point (AP) at homes, schools, or offices. When multiple APs are deployed in the network field, the proper transmission power of each AP is essential to improve the performance, considering the coverage area, transmission capacity, and interference. In this paper, the authors study the transmission power optimization of concurrently communicating two APs in WLAN. Based on extensive experiment results, the authors propose a method of selecting the best power for each AP from the signal-to-noise ratio (SNR) of receiving signal strength (RSS). For evaluations, the authors implemented the proposed method on the elastic WLAN system testbed using Raspberry Pi for APs and conducted experiments for nine network topologies in two buildings at Okayama University. The results show that the proposal always selects the best power in any topology.

No abstract

Currently, the IEEE 802.11n wireless local-area network (WLAN) has been extensively deployed world-wide. For the efficient channel assignment to access-points (APs) from the limited number of partially overlapping channels (POCs) at 2.4GHz band, we have studied the throughput drop estimation model for concurrently communicating links using the channel bonding (CB). However, non-CB links should be used in dense WLANs, since the CB links often reduce the transmission capacity due to high interferences from other links. In this paper, we examine the throughput drop estimation model for concurrently communicating links without using the CB in 802.11n WLAN, and its application to the POC assignment to the APs. First, we verify the model accuracy through experiments in two network fields. The results show that the average error is 9.946% and 6.285% for the high and low interference case respectively. Then, we verify the effectiveness of the POC assignment to the APs using the model through simulations and experiments. The results show that the model improves the smallest throughput of a host by 22.195% and the total throughput of all the hosts by 22.196% on average in simulations for three large topologies, and the total throughput by 12.89% on average in experiments for two small topologies.