Interconnection Issues in a Multivendor Enviroments

Problems associated with a Multi-vendor Environment and How to deal with it in a Cellular Network.

In today’s networks, whether GSM, WCDMA and CDMA whether it is 3G or 2G, there are a number of challenges arising when a particular operator chooses multiple vendors to supply its telecoms equipment.
Ideally, there should be a smooth and seamless interconnection amongst the vendors going by the standardization of almost all the interfaces.
In practice, this seamless interconnection faces a number of challenges which I intend to discuss here.

I will like to categorize these problems as arising from
1. A interface problems
2. MSC-MSC connection problems
3. IN problems
4. HLR issues


A- Interface Problems
When vendor A’s MSC connects to Vendor B’s BSC a number of issues arise from this connection.
Ordinarily, the A interface is a standard interface and this should not pose a problem at all. But there exist some.
Below is a typical GSM network and I will use this for this discussion.



A typical network structure


Commonly the interconnection facility between the MSC and the BSC is an E1. This E1 are structurally numbered between the MSC and BSC and there has to be agreement between the two on how this numbering should be carried out. Once this is agreed, it is expected that this connection will work.
But there exist one simple problem called error checking method between the two network entities. This defines the way errors will be responded to along the link.
Most vendors will by default configure there error methods as Basic method by default while others will choose PCR method. These are typically MTP L2 error correction and detection methods.
Don’t forget PCR stands for Preventive Cyclic Redundancy.
On a general principle basic method is used on a normal terrestrial transmission because it is much more efficient, while PCR should be used for a satellite transmission link. PCR uses constant retransmission rather than error checking. With Basic error detection/correction, when an error is detected, a retransmission is requested. The sequence number is provided for the last received good signal unit enabling the originator of the bad signal unit to determine which one to re-retransmit.
In PCR, all transmitted signal units are retransmitted automatically during ideal periods until until they are acknowledged. Once acknowledged, they are dropped from the transmission buffer
Once there exist a disagreement on the error method, the link will not function properly and in some instances will not work at all.


The E- Interface MSC to MSC

This is by far the most straight forward interface please bear in mind that the error checking method also.
Here standard SS7 Protocol applies with ISUP signaling at the upper level for call control and Setup. I have not encountered any major problem here and it may interest your to know the MSC’s I have been involved in their interconnection.
ZTE----ERICSSON
ZTE-----HUAWEI
ZTE-----SIEMENS
ZTE-----NOKIA
ZTE-----NORTEL
In these, if you follow standard procedures the interconnection is fairly straight forward.

C- Interface MSC to HLR
It is important to take not of the MAP protocol level supported by both MSC and HLR.
Problems may also exist in USSD data and communication. Therefore supported CAMEL phase by the HLR is of real importance

MSC-IN interface
I have encountered numerous problems here but won’t like to discuss some of them and the solution here but if you are having issues with it right now just call me on +2348082700056. Well it is just for free consultancy ok

I hope this is of some help but if you think it is scrap just let me know. Cool!