Let us do a quick review of a typical WiMAX network architecture: Essentially, the MS (member station)/SS (subscriber station) is on one side, and the BS (base station), ASN (Access Service Network) Gateway, CSN (Connectivity Service Network: HA(home agent), AAA, etc.) is on the other side. Please remember the following common interface terminologies: the air-interface between the MS to BS is termed R1, the interface between MS to CSN is R2, BS to ASN is R6, ASN to CSN is R3, ASN to another ASN is R4 and CSN to another operator’s CSN is R5. Next, we provide a simplistic summary of the network entry and initialization process: Phase a) the MS scans the DL channel and synchronizes with the BS, Phase b) transmit parameters are obtained, Phase c) ranging is performed, Phase d) basic capabilities are negotiated, Phase e) MS authorized and public keys exchanged, Phase f) MS registration performed, Phase g) IP connectivity established, Phase h) time of day established, Phase i) operational parameters transferred, and Phase j) connections setup. Now, if you recall our aforementioned interface terminologies (R1, R3, R6, etc.), Phase a) through Phase d) can be categorized into the R1 interface, and Phase e) through Phase j) can be categorized into the R3 and R6 interfaces. Our focus for a first pass network entry assessment is mainly on the R1, R3 and R6 interfaces. From an OSI (Open System Interconnection) model perspective, our focus is on layer 1 (physical layer), layer 2 (data link layer), and layer 3 (the network layer). There are several commercially available network monitoring tools which are specifically designed for 1) functional verification (protocol monitoring along R1, R6 and R3, etc.), 2) performance verification (MAC layer of BS when connected to more than one MS, ASN-GW under loaded conditions, etc.), and 3) live network testing. In a green field deployment, these tools can quickly and effectively identify the root-cause of problems in the initial setup of the BS/ASN/CSN (AAA, etc.). Once basic network entry is made and an IP address is obtained by the MS, a quick speed test can be performed. To gain an accurate measurement of the DL/UL speed between MS and BS, it is advisable to build an independent performance server using a notebook PC (e.g. containing Speedtest APs) and place the PC server at the CSN.
Some well known network monitoring tools include Wireless Logix Group’s XCAL Tool (this is installed on the MS (embedded WiMAX PCI Express Mini Card, WiMAX USB dongle, etc.) and provides the operator an accurate view of the RF performance (CINR, RSSI, etc.) from the client device point of view), Sanjole Corporation’s Wavejudge 4800/4900 (over-the- air R1 monitoring and much much more, etc.), Tektronix Communication’s NSA – network and service analyzer (R1, R3, R6 monitoring, etc. while placed onto a BS port), and open-source Wireshark network protocol analyzer (which mainly looks at the transport layer, etc.). The operator can also monitor the WiMAX conversation by observing back-end session logs at the CSN. In any case, the fundamental handshake between client (MS/SS) and network (WiMAX BS) must be proven out, and once this is achieved, the green field operator can advance to the next level of exhaustive IOT testing.
