Sponsored by the National Science Foundation

WiMAX Campus deployment Status & measurements

Thanasis KorakisPolytechnic Institute of NYU

July 27, 2011

Sponsored by the National Science Foundation 2

Base Station Configuration

• The BS (server, IDU) have been installed in the network room of the Library in the ECE Dept Building (5 Metrotech Center).

• The BS server uses the WiMAX RF Agg Mgr to control access and set BTS parameters. The software is updated regularly to the latest release.

• The outdoor parts (sector antenna, GPS antenna, ODU) have been installed on the roof of the ECE Dept Building (5 floor building).

• The network is up and running on a regular basis since September 2010.

• WiMAX experiments are conducted using different devices such as Beceem USB Dongle with Windows and Dell Linux netbooks with internal Intel WiMAX card.

• WiMAX-equipped clients are integrated in OMF testbed so that researchers can run WiMAX experiments via OMF.

Sponsored by the National Science Foundation 3

Range and Throughput Experiment Configuration

• To gather throughput statistics, we used Bittorrent rather than traditional network testing tools (e.g. iperf)

– Behavior of a TCP flow, as measured by iperf, gives pessimistic picture of network performance: link under-utilization, poor recovery from loss, highly variable results between iperf trials, and overall degraded end-to-end performance. Each measurement point takes some time to collect, so this tool is not suitable for taking hundreds of measurement points over a wide area.

– Bittorrent uses multiple parallel connections to maximize link utilization, and DL and UL speeds stabilize quickly as link quality changes while we move throughout the coverage area.

BS tx power = 38 dBm

Sponsored by the National Science Foundation 4

Main Execution Loop of Measurement Script

• Python script to aid in efficiently collecting range and throughput measurement points over a wide area. The script will be ported to C so as to make use of OML libraries.

Sponsored by the National Science Foundation 5

Results

• Maximum throughput: 1Mbps UL, 17Mbps DL

• Throughput grows linearly with RSSI, CINR; more loosely correlated with distance from BS due to the presence of buildings and other obstructions.

• Cell radius: ~0.5 km• Performance

deteriorated at long distances and without clear sight to the BS. 

• Further measurements are being taken to observe the behavior of different transport layer protocols and the effect of ARQ on network performance.