Wireless network analysis-vsat,wlan,wimax,gsm,cdma,lte
This page describes wireless network analysis basics which can be applied to any network as per vsat,wlan,wimax,gsm,cdma and lte technologies/standards. It covers tools used for troubleshooting by developers and network engineers across the world.
This generic guide of wireless network analysis will help find solutions to the problems or issues related to these wireless technologies.
VSAT Network Analysis
VSAT is used as transmission system for providing voice and data connectivity to remote areas. These remote areas are not feasible to lay copper cables and fiber optic cables. VSAT stands for Very Small Aperture Terminal. VSAT system usually will have two parts viz. outdoor part and Indoor part. The outdoor part composed of antenna and RF subsystems(RF ODU, PA, LNA). Indoor part composed of mux-demux, modem and small exchange (PBX). There are two topologies viz. star and mesh. Star system consists of VSATs and a hub station. Mesh system consists of VSATs with larger antenna. There is no hub station in mesh network.
There are various RF bands of operation in VSAT viz. C band, Ku band, Ka band etc.
VSAT network analysis requires knowledge of RF part after installation. The VSAT network engineer need to have spectrum analyzer to monitor the RF frequencies allocated to different VSATs and Hub station. This helps to know if any VSAT station is powered on and transmitting the carrier or not. If the RF signal is not visible in the spectrum analyzer then the VSAT is either off or have got some problem in RF part (RF ODU or power amplifier).
There is a way to verify receiver part by checking received RF signal strength in modem or in spectrum analyzer. Another important parameter is Eb/No or CNR to be checked in the modem. Based on BER and modulation type, different CNR(or Eb/No) is required for the VSAT system to work efficiently.
Other equipments needed for frequency stability testing is frequency counter. To measure absolute power level power meter will be very useful.
WiMAX Network Analysis
WiMAX system is mainly designed as replacement of existing wired line internet technologies such as ADSL. This system composed of two subsystems viz. subscriber station and base station. The system works mainly based on TDD frame concepts where in downlink transmission of base station and uplink transmission of subscriber station will use the same frequency at different time instants.
Wimax network analysis requires over the air protocol analyzer. RF spectrum analyzer will help analyze RF issues if any.
WiMAX subsystems(SS and BS) will composed of multiple layers in a protocol stack. It includes PHY, MAC and upper layers. For PHY layer analysis, various test and measurement applications are developed which will work with or without RF hardware. For MAC and upper layer protocol analysis MAC sniffer and protocol analyzers compliant to wimax standard have been developed. The real time wimax signal analysis requires sophisticated real time spectrum analyzers. RSA 3408A from Tektronix is used for this.
WLAN Network Analysis
WLAN network consists of access point (AP) and stations (STAs). They can communicate using dipole antennas wirelessly. AP is also referred as WiFi or WLAN router. WLAN protocol stack also consists of RF, PHY, MAC and upper layers. RF and PHY layers are tested using test and measurement tools. For MAC and upper layers protocol analyzer and/or network analyzer is needed. There are various standards developed under WLAN family e.g. 11a, 11b, 11g, 11n, 11ac, 11ad etc.
GSM Network Analysis
GSM network composed of mobile subscribers, BTS, BSC, MSC, backbone connectivity for voice and data transport etc. GSM network analysis is divided into mobile (MS) analysis and base station analysis. Protocol analyzer, RF signal generator and analyzer and network analyzer is need for GSM signal analysis. The companies working in GSM stack development usually develop their own debugging applications for mobile and network log analysis.
BER analyzers are also used as performance benchmarking of these wireless systems end to end for short term and long term stability tests. The above concepts can also be applied to CDMA, LTE, LTE Advanced, TD-SCDMA and other wireless networks too.