Architectur and QoS Model in Convergence 2G - 3G and 4G In IP Access Network Mr GOUGIL Lhoussaine Télécommunication Engineer And Doctoral student Laboratoire LSIS ; ENSA Fès ; Université USMBA lgougil@hotmail.com Mr Mostafa MRABTI Laboratoire LSIS ; ENSA Fès ; Université USMBA mostafa.mrabti@yahoo.f Abstract Currently, all mobile services converge to unique IP access network with the All IP trend, all of the 2G and 3G mobile services will be migrated to the IPRAN network, and the LTE evolution is an evolution towards an all-ip architecture and is seen as one of the important incentive for the adoption of IP/Ethernet in the backhaul. This document intends to describe the design of access layer and propose a model for integration QoS Model in convergence I. INTRODUCTION Actualy the current trend of mobile 2G-3G and 4G is the convergence technologies 2G -3G and 4G coexistence in one IP acces network IP RAN also the attendance is to have the unique RAN : Single RAN. The Single RAN solution and devices will offer more capacity, and more value added services to end users. Currently, the major network only carries the 3G CS+PS traffic (2G traffic is carried in TDM network). With the All IP trend, all of the mobile services will be migrated to the IPRAN network, especially the 2G mobile service, which is being carried by TDM network currently. All of the mobile service will also be migrated to MPLS Core and reach the Core Network by IP. The LTE/EPC evolution is an evolution towards an all-ip architecture and is seen as one of the important incentive for the adoption of IP/Ethernet in the backhaul. The LTE/EPC evolution will push more intelligence further out into the RAN and onto the enodebs with direct interfaces (X2), and requires an any-to-any relationship between the radio and core nodes Data network designers are concerned with the ratio of over-provisioning, while radio network designers focus on quality of service. IP RAN and QOS design needs to fulfill both these world-views at the same time. The micro and macro angles are very much in the spotlight here regarding how to achieve quality for the service while supporting a good business model. II NETWORK ARCHITECTURE II.1 3G And 2 G Network Architecture evolution In first age of 2G and 3G the traffic between the BTS / NodeB and BSC-MGW / RNC are assured by TDM network In the traditional, second and third-generation (2G, and 3G) Radio Access Network (RAN) architecture, where each cell site node is connected to a central aggregation node, the backhaul network portion access - or last mile - has a huband-spoke design. This means that there has been no reason to use Layer 3 in that part of the network Figure-1 Old architecture
With development of new technologies and because the need of bandwidth, we construct new network based in IP called IPRAN and we migrate the access radio to this new architecture. The extension of ring topologies, especially in metropolitan areas. This migration to direct communication is a good reason implemented Layer 3 technologies, not only in the aggregation, but also in the access portion of the RAN backhaul network. The initial deployment of Layer 3 in the backhaul demonstrates its flexibility by reducing the traditional operational time for radio network upgrade and rehoming In the IPRAN network carries the 3G traffic from NodeB to RNC, 3G Traffic reach the RNC through Iub interface. For voice is running in TDM Network. The 2G service, in some case is it is running in TDM network and other case in IP In the MPLS Core, only the 3G PS traffic is carried by IP network while other services, such as 3G CS, is carried by the ATM network. Figure-2 Current Architecture III E2E SERVICE III 1-2G/3G Services 1- CS Service MBTS generates the 2G/3G CS traffic and reaches the MBSC Abis/Iu_b interface via the IPRAN network. If the traffic is the CS signal, MBSC will attach the VLAN tag of signal and send it to MSC in core network via the VPN tunnel in MPLS network. If the traffic is the media, MBSC will attach the VLAN tag of media and send it to MGW in core network via the VPN tunnel in BBIP. 2-2G/3G PS Service MBTS generates the 2G/3G PS traffic and reaches the MBSC Abis/Iu_b interface via the IPRAN network. If the traffic is the PS signal, MBSC will attach the VLAN tag of PS signal and send it to SGSN in core network via the VPN tunnel in MPLS network. If the traffic is the PS media, MBSC will attach the VLAN tag of media and send it to GGSN in core network via the VPN tunnel in MPLS network. 3- Iur Service Iur traffic is for the communication between two MBSCs. When the mobile subscriber is traveling across different area, the 2G/3G service will switch from MBSC1 to MBSC2. To make sure the switch works smoothly, the Iur is vital. MBSC is connecting to BBIP Core and the Iur service is carried by VPN tunnel in Backbone IP network. II.2 -Target Network Architecture : Single RAN Architecture III-2-4G Services The Figure 2 below shows that with single RAN we have 1 device for Node B and BTS are in the unique equipment MBTS Figure 3 Single RAN Architecture
There are several types of traffic supported from the enodeb. Each could have different transport, connectivity, and security requirements and will be directed toward different parts of the network. The types of traffic include: enodeb uses the S1-AP protocol on the S1-MME interface with the Mobility Management Entity (MME) for control plane traffic. enb uses the GTP-U protocol on the S1-U interface with the Serving Gateway (S-GW) for user plane traffic. Collectively the S1-MME and S1-U interfaces are known as the S1 interface, which represents the interface from enb to the EPC. Figure 2 LTE traffic classes in TS 23.203 IV 2 Qos overview enodeb uses the X2-AP protocol on the X2 interface with other enodeb elements. OSS (operations support system) traffic destined for core applications that provide fault, configuration, and performance management Network Synchronisation traffic IV- QOS DESIGN IV -1 SLA of Network Based on the solution provided by IP RAN network is able to achieve the Wireless Service KPI Requirements 3GPP Traffic Type Common Channels, SRB Voice Delay Service KPI Requirements Jitter Lost Video Streaming trafic Interactive Trafic 60 ms 40 ms 1.00% Background Trafic 60 ms 40 ms 1.00% Table 1 Service KPI Requirement The figure2 GPP define the KPI for services as : In IP-based networks, differentiated service is performed on a per-hop basis. The most common techniques used are Differentiated Services (DiffServ, RFC 2474, RFC 247, RFC 3260), which uses the 6-bit DSCP field in the IP header, and MPLS, which also uses the DiffServ architecture, but with different marking techniques (RFC 3270). In particular, MPLS supports 3-bits (8-levels) in the EXP field. In 3GPP, the QoS Class Indicator (QCI) maps directly to DSCP. The basic classes defined by DiffServ are default, expedited forwarding, and assured forwarding. Of these, expedited forwarding is used for strict priority (e.g., video and voice), and assured forwarding is used for business differentiation (e.g., weighted-fair priority). For the 3G - 4 G Ethernet service, the Node B- ENode B side will use one VLAN to access the IP RAN network; the different class of services will be marked as both different VLAN 802.1p value and IP DSCP value. When the node B traffic upstream traffic is encapsulated with MPLS labels, the VLAN priority will be mapped to MPLS exp value. For the Node B downstream, the VLAN 802.1p priority value will be mapped from MPLS EXP. For the RNC-MBSC-MME/SGW if there is no VLAN encapsulation for the traffic between this equipment and IPRAN Routers. il will mark different class of services by different DSCP value in the IP header. For RNC upstream traffic, when the traffic is encapsulated with MPLS label, the IP DSCP valuewill be mapped to MPLS EXP value. For the
downstream, when the MPLS label is removed, the EXP value will be mapped to IP DSCP again. In this style, the QOS can be deployed end to end. The illustration about the 3G 4 G QOS is given below III - Qos Design for convergenace IP architecture : 2G 3G and 4G. 4G - LTE networks have more traffic types than 3G networks, because all traffic is transported natively as IP packets. GTP tunneling exists, but all services and thus traffic runs over the IP network. LTE traffic types can be divided into two groups: control plane and signaling, and user traffic. On 4G - LTE networks, a vast amount of signaling and control plane traffic passes through the IP network compared with the packet-based network portion of 3G networks. Control plane and signaling traffic can be direct, indirect, or something in between. The underlying transport will need to support traffic prioritization, dual-priority and low-latency queues for 3GPP compliance table 3,. Hierarchical QoS (H-QoS) is needed to support the GBR and MBR classification types and also so that important traffic types can be prioritised for multiple different cell sites under congestion conditions. H-QoS is important to manage contention in the last mile, by representing last-mile available bandwidth at the aggregation and distribution level. Work is ongoing in relation to the bandwidth feedback mechanisms, and protocols such as Access Node Control Protocol (ANCP) are under consideration. III-1 Congestion management and avoidance When congestion occurs and becomes severe, the special queuing and the packet drop policy can be adopted to trade off the resources assignment among various forwarding services (such as EF and AF). The common packet drop policies include Tail Drop, Random Early Detection (RED), and hted Random Early Detection (WRED). Service of class WFQ weight value AF1 AF2 10 AF3 AF4 40 BE Table 3 the WFQ scheduling planning table Color lowlimit Highlimit Discardrate QoS Requirements The LTE evolution does introduce new concepts, including: QoS Class Identifier (QCI): Scalar that controls bearer level QoS treatment; the current specifications have defined 9 QCI values (3GPP TS 23.203). Guaranteed Bit Rate (GBR): Bit rate that a GBR bearer is expected to provide Maximum Bit Rate (MBR) Limits the bit rate that a GBR bearer is expected to provide Allocation and Retention Priority (ARP): Controls how a bearer establishment or modification request can be accepted when resources are constrained green 80% 100% 30% yellow 70% 90% 40% red 60% 80% 0% Table 4 WRED proclicy III- 2 QOS MODEL Studying all constraint and KPI need for each mobile services we propose the module for IP mobile convergence network and heterogeneous IP mobile networks. The proposed architecture aims at achieving highly efficient resource utilization in the IP-based backhaul network in order to support high speed data services voice and others. The
proposed QoS architecture has been designed to be consistent with the 2G- 3G and 4G network architecture evolution. IV- Conclusion Services DSCP E X P Queue Future-reserved 111000 7 CS7 (PQ+ (CS7) Network Protocol & Signal 110000 6 CS6 (PQ+ (CS6) 4G Voice, 3G Voice, VOIP, fixed voice IMS Signaling 101110 3G ATM VBR service (EF) (voice & stream) BTV VoD 4G conversational/streaming Real time gaming 4G R99 CS/PS conversational/streaming HSPA conversational/streaming 3G ETH OAM 100010 (AF41) Reserved. 011010 (AF31) Reserved. 010010 (AF21) Network management 001010 (AF11) TCP Based : www, FTP, P2P Enterprise VPN (xdsl) 0(defau lt) Table Service QoS priority Band widt h Tail drop) 2% (PIR) Tail drop) EF (PQ+ Tail drop) 4 AF 41 (WFQ 3 AF31 (WFQ + wfq) 2 AF21 (WFQ 1 AF11 (WFQ 0 BE (WFQ + WRED) 80% (PIR) 40 10 802.1P 7 6 4 3 2 1 0 We present in Table the QoS models with respect to providing an appropriate mapping of traffic types to traffic Classes. And then conversely, by providing a flexible architecture afford guaranteed and differentiated quality for traffic flows in the network by raising priority of certain flow or limiting the priority of another traffic flow This model allows a large number of applications to share the EF class. Consequently, voice traffic can share its queue with other, potentially bursty video and TCP traffic. In an heterogeneous IP network REFERENCES 1-Considerations for Backhaul of 2G/3G and Long Term Evolution Architectural----2010 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information 2-4G Americas Coexistence of GSM HSPA LTE May 2011 3-Public Safety LTE Septembre 2010 Alcatel Lucent 4 - LTE MAC Scheduler & Radio Acess Bearer Roke Manor Research 2011 -Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers 6-3GPP TS 23.401 Standardized QCI Characteristics