There is two systems of connection for the sites used in zain 2G and 3G, 2G is the old type of connection which is still used the BSC connected to the MGW then connected to BTS,BTS connected to SIU to be over IP (OIP) , the BSC also connected to MSS but connected to transcoder before connected to MGW then connected to MSS , BSC and transcoder may be in the same place or in separated places ,there is a cards inside of the BSC called PGW which is responsible for the traffic and there is others called NWI responsible for switching of input and output IPs, and the BSC also connected to OSS ,SGSN and OSR .

      3G is the new type of connection which is used RNC instead of BSC and RBS(NodeB) instead of BTS and in this type it used OML for each RBS and there is OML between RNC and the juniper, and there is heartbeat failure alarm for each site(RBS) down not like 2G because the heartbeat failure appear just when the BSC down because RNC connected to each RBS ,there is no alarms like open door or ac failure unit or aviation light failure in 3G because  all of them connected in 2G system ,sometimes in 3G they linked the sectors in AB method which is allow working with two frequencies GSM and DCS one of them 900MHz and the other is 1800MHz then when we check the site is look like we have 6sectors but we have just three every one used two frequencies  and in 3G system we can enter into any RBS remotely not like 2G is more difficult we should set programs and components to make it available ,the signal that coming from RBS to the juniper should linked before to the SIU to be over IP (OIP) then to transmission  then to the juniper then the juniper linked to OSR and OSS which is used for  remotely login to the sites, the juniper also connected to RNC by two types of links: Ethernet link for OML and there is one or two optical fiber links for call and packets (signal and traffic) ,they used two fiber cables when there is a big traffic, one cable can't handle it ,one cable for the sites and their signal and the other for calls and data.