It starts to be a common request from the network operators to share a common transport for multiple radio technologies in Radio Base Stations, RBSs, with multiple radio technologies with data traffic belonging to the same QoS class from each technology.
RBSs are developed to be placed both inside and outside buildings for serving the users and their telecommunications equipment. The casing of an RBS can contain both antennas and telecommunications circuitry. Further, the antennas and telecommunications circuitry is designed to serve a number of different Radio Access Technologies, RATs, such as WCDMA (Wideband Code Division Multiple Access), GSM (Global System for Mobile Communications), LTE (Long Term Evolution), Wi-Fi (Wireless Fidelity, also abbreviated WIFI, WI-FI, WiFi). The backhauling is based on the Internet Protocol, IP. Thus, despite RAT, all transfer of the data packets will be performed over an IP infrastructure instead of multiple, parallel dedicated network structures that are technology adapted. The one and same IP infrastructure solution has a number of advantages, e.g. simplicity, known technology, low investment costs, over a solution where each RAT is served separately resulting in separate wiring or packet infrastructure from each RBS. Thus, all data packets will be forwarded on the same wire or in the same optical fibre and packet infrastructure irrespective of the RAT a data packet originates from.
The design of the RBSs provides the possibility to cascade a number of RBSs. Each RBS is therefore provided with a switching/routing possibility. However, in a scenario wherein a large number of RBSs are aggregated in the network, and a large number of user equipments are active at the same time, this might result in congestion in the data traffic.
In small cell networks IPsec is commonly used. In one IPsec tunnel, there can be several type of radio traffic. The problem with the heterogeneous networks using IPsec is that the traffic is classified and treated in a same way, without any consideration of traffic characteristic or the type of radio access, e.g. LTE, WiFi, 3G.
Tests of congestion situations have shown that if the same Quality of Service, QoS, class is used for data packets to/from different RATs, normal scheduling will not forward data packets in a fair manner irrespective of the RAT that the data packets originate from when the data traffic from different RATs are mixed on the same wire and in the same IPsec tunnel. In the tests, the Best Effort QoS class was used for all data packet traffic. Instead of an equal and fair distribution of data packets using only a QoS based scheduling, the result became an uneven distribution between radio technologies.
Different radio access technologies such as 3G, LTE, and WiFi have different delay between the UE and application server, due to the Round Trip Time (RTT) being different depending on the radio access technology. The reason for different delay in different radio access technologies is caused by the termination point of the radio protocols as well as different radio characteristics. In 3G the Radio Network Controller (RNC) is involved in termination of radio protocols, in WiFi the access points terminates radio protocols.
There is no existing solution for accomplishing fairness between data packets originating from different access technologies when transported in an encrypted tunnel. It is impossible for the scheduler to detect and schedule data traffic flows from different technologies having the same QoS class, i.e. Quality of Service class.