Abstract
At a time when the existing mobile data network based on GSM standard no longer meet the current needs of customers for its high-speed performance, it is necessary to build a network of new generation mobile communication, which, unlike its predecessors, was originally designed to take account of priority of data transmission. These networks are called networks of 3rd generation, which includes standards for CDMA 2000 and WCDMA.
To increase the speed of data transmission in the standard CDMA 2000 using an add-on called EVDO (Evolution-Data Optimized), which allows you to reach peak speeds of 2.4 Mbit / s (at an average of about 300-500 kbit / s) in canal «down» and to 153 kbit per s in the channel up. This delivers the best use of radio frequency resource - the spectral efficiency of up to 1.6 Mbit / MHz. The gain in data transfer speed achieved by the temporary separation of the channel from the operator to the caller. However, increasing the speed of data transmission using EVDO leads to the impossibility of providing voice services.
The purpose of this master's work is to study and optimize the characteristics of high-speed data transmission networks through the integration of a segment of wireless local area networks WLAN.
Objectives of work:
- Development of two-dimensional model CDMA2000/WLAN network;
- Study the characteristics of the developed model;
- Select method of optimization of the network;
In the face of fierce competition, operators need to look for ways to improve the quality and quantity of their services. The plan to integrate the most promising segments of WLAN (wireless local area network - wireless LAN) networks in the structure of the network CDMA. This would eliminate the drawbacks (low speed and lack of mobility CDMA WLAN) and combine advantages (greater mobility CDMA and high-speed WLAN).
There are two approaches to combine CDMA and WLAN networks, it is tightly-coupled and loosely-coupled.
Tightly-coupled Interworking
The rationale behind the tightly-coupled approach is to make the WLAN network appear to the 3G core network as another 3G access network. The WLAN network would emulate functions which are natively available in 3G radio access networks. In this architecture, utilized by WISP No.1 in Figure 3, the “WLAN gateway” network element introduced to achieve integration appears to the upstream 3G core as a Packet Control Function (PCF), in the case of a CDMA2000 core network. The WLAN gateway hides the details of the WLAN network to the
3G core, and implements all the 3G protocols (mobility management, authentication, etc.)
required in a 3G radio access network. Mobile Nodes in this approach are required to implement
the corresponding 3G protocol stack on top of their standard WLAN network cards, and switch from one physical layer to the next as needed. All the traffic generated by clients in the WLAN network is injected using 3G protocols into the 3G core network. These networks would share the same authentication, signaling, transport and billing infrastructures, independently from the
protocols used at the physical layer on the radio interface.
The configuration of the client devices also presents several issues with this approach. First, as described earlier, the WLAN cards would need to implement the 3G protocol stack. It would also mandate the use of 3G-specific authentication mechanisms for authentication on Wireless LANs, forcing WLAN providers to interconnect to the 3G carriers’ SS7 network to perform authentication procedures. This would also imply the use of WLAN cards with built-in 3G credentials. For the reasons described above, the complexity and the high cost of the reconfiguration of the 3G core networks and WLAN gateways would force operators that chose the tightly-coupled approach to become uncompetitive to WLAN-only ISPs.
Loosely-coupled Interworking
Like the previous architecture, the loosely-coupled approach calls for the introduction of a new
element in the WLAN net- work, the WLAN gateway. The user population that accesses
services of the WLAN gateway may include users that have locally signed on, as well as mobile
users visiting from other net- works. We call this approach loosely-coupled interworking because
it completely separates the data paths in WLAN and 3G networks. The high speed WLAN data traffic is never injected into the 3G core network but the end user still experience seamless access.
In this approach, different mechanisms and protocols can handle authentication, billing and mobility management in the 3G and WLAN portions of the network. However, for seamless operation to be possible, they have to interoperate. In the case of interoperation with CDMA2000, this requires that the WLAN gateway supports Mobile-IP functionalities to handle mobility across networks, as well as AAA services to interwork with the 3G’s home network AAA servers. This will enable the 3G provider to collect the WLAN accounting records and generate a unified billing statement indicating usage and various price schemes for both (3G and WLAN) networks. At the same time, the use of compatible AAA services on the two networks would allow the WLAN gateway to dynamically obtain per-user ser- vice policies from their Home AAA servers, and to enforce and adapt such policies to the WLAN network.
Conclusion and outlook studies
Integrated services WLAN/CDMA2000 undoubtedly be of benefit to both operators, and subscribers. And the approach «weak» interaction will allow for the integration of the two networks the most painless and least costly material. Thus, the use of Mobile IP will provide easy access and smooth transition between the two networks.
To join the networks you want to deploy WLAN in a network that supports Mobile IP and authentication protocols used in CDMA networks.
In the future will create a model of the two networks, as well as will be appreciated by those of its characteristics as bandwidth, the probability of denial in the service and handoff, the optimal location of base stations and WLAN networks segments on the placement of subscribers.
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