GPRS Troubleshooting

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Basic Flowchart

Does the phone show service at all?

The phone must be able to complete a normal location update before making a GPRS connection. If the phone does not register to the network at all, that problem must be corrected before trying to use GPRS.

Do phone calls work?

If the phone can register, but has poor call quality, that is a sign of Radio Related Problems. Resolve those first, because they will impair GPRS performance and make further troubleshooting difficult.

Does the phone show up in the "mbts gprs list"?

If no phones appear in “mbts gprs list”, check to see that the number of channels allowed for GPRS is at least as many as the number of channels is it actually trying to use.

Does the phone have an IP address?

Look at the “IPs=“ parameter for the phone’s entry in "mbts gprs list -v”. Is the value an IP address or just “none”? Without an IP address, the phone cannot connect to the internet.

Check the GPRS/GGSN IP address pool.

Check to see that the GPRS client address pool is something other than 127.0.0.1. The address range should be a private address range or a public range that is routable from the machine running YateBTS. The pool is normally 192.168.99.1-192.168.99.254.

Check the APN on the phone.

The phone needs at least one “APN” (Access Point Name) defined in its GPRS configuration. If there is no APN defined, the phone will not request an IP address. YateBTS does not actually look at this APN, so it can be just about anything, but at least one APN must be defined.

Check the GPRS link quality.

In "mbts gprs list -v”, check that the uplink and downlink frame error rates are both < 5%.

Is DNS working?

Are the phone’s DNS requests going to a valid server? Are the requests being answered? Check to see that the GPRS DNS addresses are configured with valid servers.

Are packets routing in both directions?

While trying to load a web page, take a look at the IP packets to and from the phone with “tcpdump -nn -i sgsntun”. If there is uplink traffic, but little or no downlink traffic, that probably indicates a routing or firewall problem. The most common cause of this problem is misconfigured or unconfigured NAT in the machine that is running YateBTS.