Discussion on Construction of CDMA2000 1x EV-DO Network

1 Overview of 3G CDMA Series

CDMA2000 1x EV-DO (Data Only)  indicates that the technology supports data only but not voice service. The 3GPP2 standardization organization has named it HRPD (High Rate Packet Data).

As shown in Figure 1, currently the standardization of CDMA2000 1x EV-DO has been completed. The air interface standard for CDMA2000 keeps developing towards Release C and Release D. The Release D version will be completed in September 2003, which will be the standard for CDMA2000 1x EV-DV(Data and Voice). CDMA2000 1x EV-DO and CDMA2000 1x EV-DV are jointly called the 3G standard of CDMA series.

2 Network Architecture of  CDMA2000 1x EV-DO

The voice core networks of IS95 and CDMA2000 1x are both based on the ANSI-41 network architecture. The core network of CDMA2000 1x EV-DO is based on wireless IP network architecture. The traditional MSC/HLR/AC are no longer involved in the call/authentication process flow of CDMA2000 1x EV-DO.

As shown in Figure 2, AN-AAA is introduced into 1x EV-DO to perform access authentication and two new signaling interfaces are added: A12 and A13, used for authorization and switching.

There is another network architecture (phase 2) of CDMA2000 1x EV-DO and the A15 interface between ANs is primarily added  to accomplish paging across ANs.

Currently, CDMA2000 1x EV-DO equipment provided by most equipment manufacturers has been developed based on phase 1 network architecture. When two equipment manufacturers use standards of different phases to develop CDMA2000 1x EV-DO equipment, the interoperability problem will not occur. But as a matter of fact the result is that the equipment of phase 2 can not implement paging between ANs, it only functions as equipment of phase 1.

3 Networking Relationship  Between CDMA2000 1x  EV-DO and CDMA2000 1x

Because CDMA2000 1x EV-DO can not provide voice services, the DO system and 1x system must be in a superposition relation.

The CDMA2000 1x EV-DO system is compatible with CDMA2000 1x packet core network.Switching between CDMA2000 1x EV-DO and CDMA2000 1x is launched by dual-mode terminal MS/AT.

4 Brief Introduction to CDMA2000 1x EV-DV

CDMA2000 1x EV-DV is the evolution trend of wireless access network of CDMA2000 1x and provides non-real-time high rate packet data services and real-time voice and data services with peak forward rate up to 3.1 Mb/s and peak backward rate up to 1.2 Mb/s. CDMA2000 1x EV-DV is completely backward compatible with CDMA2000 1x and IS95.

It is planned that the architecture of CDMA2000 1x EV-DV core network should use an All-IP architecture, but work on its standardization is far from completion.

The CDMA2000 1x EV-DV authentication algorithm supports CAVE (Cellular Authentication and Voice Encryption) and AKA (Authenticated Key Agreement) algorithms. The parameters and algorithm of the AKA authentication are totally different from those of CAVE. Therefore, if the AKA authentication is used, a new UIM (User Identity Module) card must be used for the 1x EV-DV mobile phone; if CAVE authentication is used, then existing UIM card of CDMA2000 1x can be used.

5 Key Technical Issues

The key technical issues in upgrading CDMA2000 1x to CDMA2000 1x EV-DO by China Unicom are described as follows:

5.1 Technical Issues for CDMA2000 1x  EV-DO to adopt Set-Card  Separation Mode

Currently, international standards of CDMA2000 1x EV-DO do not support the set-card separation mechanism. Therefore, China Unicom needs to solve many special problems associated with authentication, authorization, accounting, UIM cards, user terminals, etc.

5.2 Switching Problems Between Voice and Data Services

(1)Research on trigger conditions of  switching between 1x and DO

Switching between 1x and DO is decided by MS/AT dual-mode terminal. There is no international standard for MS/AT for the moment. Therefore, network selection principles and the inter-network switching and triggering mechanism of MS/AT must be properly defined and its operation flow must be standardized.

（2）Research on how to implement concurrent services on MS/AT dual-mode terminals

The 1x network does not support concurrent services for the time being. Only the voice priority function is implemented. Its air interface and A interface cannot be upgraded together with the upgrade of 1x to DO. Therefore, the implementation scheme for concurrent services of dual-mode terminals still needs to be discussed (including the network scheme and terminal scheme).