International telecommunication union

4.2 Radio network

– IP protocols have a large amount of overhead that will reduce spectral efficiency, in particular when used for voice applications. It may also suffer intolerable delays because bandwidths for wireless mobile applications are still limited and sometimes expensive to obtain. In case of predominant IP/UDP/RTP protocol stack, the size of the combined headers is at least 40 bytes for IPv4 and at least 60 bytes for IPv6, while the voice data is typically shorter than the IP/UDP/RTP header; various header adaptation or multiplexing techniques can be therefore applied. (e.g. header compression or PPPmux).

• IP-based RAN shall support the very flexible allocation of resources among different cells and also dynamically uplink and downlink based on the unpredictable change of IP traffic over the overall access network.

• IP-based RAN shall support inter-working/interoperability of the QoS mechanism developed for the radio access network and the QoS mechanism used in the IP core network (e.g. MPLS, DiffServ).

– New parameters may be, if necessary, introduced into the QoS mechanism of the radio access network or the IP core network.

• IP-based RAN shall maximize spectrum efficiency over the air.

– Improved statistical multiplexing should be provided to support mixed services (e.g. real time variable bit rate and non-real time bursty data stream).

– Optimal source and channel coding should be enhanced for various IP multimedia applications.

• IP-based RAN architecture shall provide protocol stacks supporting a range of services with different QoS requirements in the access network.

• IP-based RAN shall enhance medium access control and radio link control (RLC) for different IP multimedia applications.

– Improved radio access and resource allocation scheme should be applied for different IP applications in medium access control. Fast uplink access procedures can be, for example, provided on the uplink and downlink for a certain type of service.

– Radio link control functions should be differentiated for each flow with more delicate flow classification (e.g. mapping of IP traffic onto appropriate radio bearer in the access network.)

• IP-based RAN shall optimize physical layer mechanisms to guarantee the quality of some applications such as voice over IP.

– Requirements for real time IP applications can be for instance applied to the optimization of physical layer mechanisms for guaranteeing QoS of the services. In this case, a couple of parameters for VoIP service (e.g. type of codec, echo control, voice packet size and de-jittering delay) can be used for the setting of coding rate, interleaving span in the physical layer; whereby the quality of voice over IP can be further improved.

• IP-based RAN shall consider interactions with functionalities of layered protocols for optimal IP packet transmission. Interactions between IP protocols (e.g. TCP) and radio protocols (e.g. radio link control) shall be in particular investigated for this purpose.

– IP protocols in conventional wired networks may be modified to be qualified for wireless access networks. For instance, typical TCP protocol interprets packet loss as congestion and erroneously reduce throughput; some solutions can be therefore applied to IP-based RAN.

– There are various control loops that will operate simultaneously by higher and lower layer protocols (e.g. TCP flow control and RLC error controls). These functions in the same protocol stack should be, hence, optimized for efficient packet data transmission.

– Radio Link Control mechanisms may consider interaction with error detection and recovery function of other lower-layered radio protocols.

– Optimal implementation of bandwidth adaptation methods in a scalable audio and video codec should be considered for spectral efficiency of the access network.

• IP-based RAN shall offer radio technologies (e.g. radio protocols and physical mechanisms) to support a variety of broadcast and multicast services (e.g. the multimedia message service and the Internet radio broadcast service).

• IP-based RAN shall support bearer differentiation capability at the access network for multiplexing different types of IP traffic over the air to achieve maximum spectrum utilization.

– Radio technologies should be optimized for different bearer at the access network. For instance, different coding and access schemes can be applied to various radio channels.

• IP-based RAN shall optimize connection admission for efficient radio resource usage in both uplink and downlink for a mixture of data flows with different QoS per IP address.

– The characterization of different IP packet data streams may be applied to connection admission function in terms of service requirements such as bandwidth and delay.

– Effects of various deployment scenarios (e.g. spectrum availability) and traffic mix such as voice and data on spectrum efficiency should be taken into account.

• IP-based RAN shall offer diverse protocol states and radio channels, and besides, fast and dynamic transition among them to support a wide range of services for different IP multimedia applications. (e.g. signalling, real time, non-real time, connection oriented and connectionless services, and combinations of these services).

– The type of the radio channels can be dynamically changed to accommodate different types of IP packet streams for the same connection.

• IP-based RAN shall support the fast resource assignment and release procedure on the uplink and downlink for some of the IP applications that are characterized as an on-off traffic pattern. (e.g. WWW browsing and FTP).

– With this feature, link utilization can increase due to non-continuous bandwidth management.

• IP-based RAN shall provide handover procedures minimizing packet loss and delay for robust and seamless IP packet transmission support.

– Lossless data transfer mechanisms should be applied to achieve the robust IP packet transmission during handover procedures of IP packet streams.

• IP-based RAN shall support advanced radio technologies that are expected to emerge in future, such as adaptive antennas, link adaptation, OFDM, software defined radio and multi-user detection.