Analisis Performansi Beberapa Wireless Access Point Tipe N Sebagai Media Transmisi Video Streaming

Wireless merupakan media dalam jaringan untuk mentransmisikan data baik berupa teks, audio, maupun video. Generasi wireless berdasarkan protokol standar IEEE 802.11 sampai saat ini telah sampai pada standar IEEE 802.11n, yang sebelumnya menggunakan standar IEEE 802.11g. Data berupa video yang di streaming merupakan data yang membutuhkan piranti wireless dengan performa yang baik. Analisis performansi wireless access point tipe n atau standar IEEE 802.11n digunakan untuk mengetahui bagaimana performa wifi dalam mentransmisikan video streaming. Piranti aplikasi VLC digunakan untuk streaming video dari server ke client. Video dengan format MP4 dan MKV codec h264 kualitas HD dan Full HD digunakan untuk menguji piranti wireless standar IEEE 802.11n. Paket-paket data dari client menuju ke sever di capture menggunakan aplikasi Wireshark. Hasil analisis pengujian menunjukkan bahwa kemampuan wireless access point dengan protokol standar IEEE 802.11n dalam mentransmisikan data berupa video streaming dengan kualitas HD dan Full HD hanya mampu menangani transmisi data tidak lebih dari empat client. Lebih dari empat client, keluaran video pada client tidak nyaman untuk dilihat. Berdasarkan pengujian, 4 buah wifi yang diuji, ubiquiti power AP N mempunyai performa paling baik

PENGEMBANGAN DAN IMPLEMENTASI ALGORITMA RATE ADAPTATION ADAPTIVE AUTO RATE FALLBACK (AARF) PADA SIMULATOR NS-3 UNTUK STANDAR WLAN IEEE 802.11N

Wireless Local Area Network (WLAN) telah mengalami perkembangan yang pesat. Pada lapisan Physical (PHY) IEEE 802.11n disediakan bandwidth kanal 20 MHz dan 40 MHz, guard interval 800 ns dan 400 ns, dan transmisi menggunakan Multiple Input Multiple Output (MIMO) menggunakan 1, 2, 3 dan 4 spatial stream. Oleh sebab itu PHY 802.11n memiliki maksimum 128 pilihan data rate dari 6,5 Mbps hingga 600 Mbps. Selain itu pada Medium Access Control (MAC)WLAN IEEE 802.11n telah ditambahkan skema pengiriman MAC Protocol Data Unit (MPDU) menggunakan Aggregate MPDU (AMDPU). Jika MPDU atau AMPDU ditransmisikan dengan data rate yang sesuai dengan kondisi kanal, maka probablitis MPDU diterima tanpa error menjadi meningkat. Sesuai penjelasan dalam standar IEEE 802.11, MAC menentukan data rate yang digunakan untuk pengiriman MPDU menggunakan algoritma rate adaptation. Beberapa algoritma adaptasi rate berdasarkan kondisi kanal khususnya untuk WLAN IEEE 802.11n telah diusulkan, namun kenaikan atau penurunan data rate dilakukan berdasarkan metode random probing yang mengakibatkan ada kemungkinan data rate yang dipilih tidak sesuai dengan kondisi kanal. Di dalam penelitian ini diusulkan sebuah algoritma rate adaptation baru yang dikembangkan dari algoritma Adaptive Auto Rate Fallback (AARF). Algoritma AARF menaikkan dan menurunkan data rate berdasarkan order probing, namun AARF melakukan probing data rate tidak berdasarkan pilihan bandwidth kanal, guard interval dan jumlah spatial stream. Oleh sebab itu didalam penelitian ini dilakukan pengembangan algoritma AARF agar dapat mengadaptasikan data rate 802.11n sesuai kondisi kanal. Pengembangan algoritma AARF-HT didalam penelitian ini dilakukan menggunakan simulator NS-3 versi 3.26 dan sesuai metode pengembangan algoritma baru pada simulator NS-3. Setelah pengujian implementasi algoritma AARF-HT pada simulator NS-3 berhasil dan tidak ada error yang muncul, kemudian dilakukan simulasi pengujian adaptasi rate algoritma AARF-HT pada WLAN IEEE 802.11n sesuai kondisi kanal. Hasil pengujian memperlihatkan fungsi pengiriman tanpa dan menggunakan skema AMPDU serta fungsi adaptasi data rate berdasarkan ukuran bandwidth, guard interval dan jumlah spatial stream pada WLAN IEEE 802.11n telah berfungsi dengan baik. Hasil pengujian juga memperlihatkan algoritma AARF-HT menghasilkan throughput yang lebih tinggi dibadingkan throughput algoritma AARF.Kata Kunci : WLAN IEEE 802.11n, Rate adaptation, AARF, AARF-HT, Simulator NS-

Adaptive delayed channel access for IEEE 802.11n WLANs

Abstract— In this paper we investigate potential benefits that an adaptive delayed channel access algorithm can attain for the next-generation wireless LANs, the IEEE 802.11n. We show that the performance of frame aggregation introduced by the 802.11n adheres due to the priority mechanism of the legacy 802.11e EDCA scheduler, resulting in a poor overall performance. Because high priority flows have low channel utilization, the low priority flows throughputs can be amerced further. By introducing an additional delay at the MAC layer, before the channel access scheduling, it will retain aggregate sizes at higher numbers and consequently a better channel utilization. Also, in order to support both UDP and TCP transport layer protocols, the algorithm’s operational conditions are kept adaptive. The simulation results demonstrate that our proposed adaptive delayed channel access outperforms significantly the current 802.11n specification and non-adaptive delayed channel access

Subjective Audio Quality over a Secure IEEE 802.11n Draft 2.0 Wireless Local Area Network

This thesis investigates the quality of audio generated by a G.711 codec and transmission over an IEEE 802.11n draft 2.0 wireless local area network (WLAN). Decline in audio quality due to additional calls or by securing the WLAN with transport mode Internet Protocol Security (IPsec) is quantified. Audio quality over an IEEE 802.11n draft 2.0 WLAN is also compared to that of IEEE 802.11b and IEEE 802.11g WLANs under the same conditions. Audio quality is evaluated by following International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation P.800, where human subjects rate audio clips recorded during various WLAN configurations. The Mean Opinion Score (MOS) is calculated as the average audio quality score given for each WLAN configuration. An 85% confidence interval is calculated for each MOS. Results suggest that audio quality over an IEEE 802.11n draft 2.0 WLAN is not higher than over an IEEE 802.11b WLAN when up to 10 simultaneous G.711 calls occur. A linear regression of the subjective scores also suggest that an IEEE 802.11n draft 2.0 WLAN can sustain an MOS greater than 3.0 (fair quality) for up to 75 simultaneous G.711 calls secured with WPA2, or up to 40 calls secured with both WPA2 and transport mode IPsec. The data strongly suggest that toll quality audio (MOS ≥ 4.0) is not currently practical over IEEE 802.11 WLANs secured with WPA2, even with the G.711 codec

Dynamic reconfiguration technologies based on FPGA in software defined radio system

Partial Reconfiguration (PR) is a method for Field Programmable Gate Array (FPGA) designs which allows multiple applications to time-share a portion of an FPGA while the rest of the device continues to operate unaffected. Using this strategy, the physical layer processing architecture in Software Defined Radio (SDR) systems can benefit from reduced complexity and increased design flexibility, as different waveform applications can be grouped into one part of a single FPGA. Waveform switching often means not only changing functionality, but also changing the FPGA clock frequency. However, that is beyond the current functionality of PR processes as the clock components (such as Digital Clock Managers (DCMs)) are excluded from the process of partial reconfiguration. In this paper, we present a novel architecture that combines another reconfigurable technology, Dynamic Reconfigurable Port (DRP), with PR based on a single FPGA in order to dynamically change both functionality and also the clock frequency. The architecture is demonstrated to reduce hardware utilization significantly compared with standard, static FPGA design

MIMO In Vivo

We present the performance of MIMO for in vivo environments, using ANSYS HFSS and their complete human body model, to determine the maximum data rates that can be achieved using an IEEE 802.11n system. Due to the lossy nature of the in vivo medium, achieving high data rates with reliable performance will be a challenge, especially since the in vivo antenna performance is strongly affected by near field coupling to the lossy medium and the signals levels will be limited by specified specific absorption rate (SAR) levels. We analyzed the bit error rate (BER) of a MIMO system with one pair of antennas placed in vivo and the second pair placed inside and outside the body at various distances from the in vivo antennas. The results were compared to SISO simulations and showed that by using MIMO in vivo, significant performance gain can be achieved, and at least two times the data rate can be supported with SAR limited transmit power levels, making it possible to achieve target data rates in the 100 Mbps.Comment: WAMICON 201