A New Global Ubiquitous Consumer Environment for 4G Wireless Communications

A key solution in facilitating the fast growth and success of any new communications environment is building the foundation for business building blocks. Currently it seems that the many downsides in wireless networking systems results from the rather constraining nature of SBM. For many access network providers (ANPs), it is the only really workable, underlying business model. However, when considered next to CBM, one could discern its weaknesses in providing the stimulus, the motivation and the glue for a real-life integrated 4G networking. For CBM to become a reality, it itself will have to have a business attraction, and not be something imposed. This will probably also have to come from outside the major cellular wireless ANPs as, initially at least, CBM may be perceived to be antagonistic to their business interests.

When addressing how to open the mobile communications environment to a wide range of new entrants, whether coming with new or old technology, whether filling niches in network accesses or provision of services, or challenging major ANPs with more modern, reconfigurable, adaptable systems, and so forth, it is clear that a new business foundation free from the constraints of the subscriber business culture is called for. In attempting to define such a new business foundation for the global wireless environment, appropriate standardization and regulatory support needs to be considered. Without such support, ensuring a global footprint for this new environment is not possible.

Since 2002 there has been significant research performed in the field of future 4G integrated networks, including architectures and business models. In 2003, a number of new projects were started within the frameworks of the European Union's Information Society Technology (EU-IST). Some examples are MOBY DICK, BRAIN/ MIND, SCOUT, ETSI BRAN, MOBIVAS, and the Academic Network for Wireless Internet Research in Europe (ANWIRE). Further research was carried out in this area by different work groups (WG) of standardization bodies and forums such as the WG2 and WG3 of the Wireless World Research Forum (WWRF), and the ITU-T NGN Focus Group (http://www.itu.int/ITU-T/ngn/fgngn). Much of this research was focused on system and service integration in heterogeneous network environments creating new integration architectures founded on an all-IP infrastructure. This characterized the main trust of ‘4G’ as perceived formally within the EU, differing in this to the definitions and perceptions of what 4G was in other economic regions. Within the ANWIRE project and the WWRF WG2 especially, some research work was supported on business models. An interesting aspect of this work was their investigations in to how to place the system users more at the centre of communication systems evolution.

In the ANWIRE project, researchers progressed this idea also by addressing the monopoly positions of the network providers -supporting the traditional subscriber-centric model-, and how this facilitated, or otherwise, the evolution and advanced development in cellular wireless networks and services. They found that regardless of the technological approach taken, in such systems, the subscribers are practically limited by the technology and service environment available with their subscriptions. For instance, the capability to use services from other service providers is inherently very limited. Such constraints have serious implications for future wireless access evolution. Much of the ANWIRE contributions on these matters have their source in the Telecommunications Research Centre (TRC) in the University of Limerick. The initial proposal for the new business model -Consumer-centric Business Model (CBM)- to remove such limitations by creating a new extra-network entity in which to locate the Authentication, Authorization and Accounting services originated from there, in 2004, (O'Droma & Ganchev, 2004). This new wireless environment entity, of which there could be many, was called the Third-Party Authentication, Authorization and Accounting Service Provider (3P-AAA-SP). The original model was later refined in (O'Droma & Ganchev, 2007). Also in the ANWIRE project, a Generic ANWIRE System and Service Integration Architecture (GAIA) was proposed and elaborated, (Ganchev et al., 2006); it was specifically referring to it as a new 4G architecture as then understood within the EU thinking. How this could form a basis for CBM was elaborated there. GAIA employs the principles of the "always best connected and best served" (ABC&S) paradigm (Ganchev et al., 2006). The ideas were further refined and re-positioned less as a specifically 4G technology and more as a new wireless communications environment and business foundation for 4G and for further wireless technological generations. Given, among other reasons, its radical placing of the user at the centre and the user-empowerment with normal consumer attributes unavailable to subscriber-users, this wireless environment was called a Ubiquitous Consumer Wireless World (UCWW), (O'Droma & Ganchev, 2007).

THE IMPACT OF 4G ON OTHER SYSTEMS

The impact of 4G is obvious on contemporary wireless broadband services. Many researchers think that the 4G system would be nothing but a modified version of WiMAX due to the similarities in the architecture to a large extent, and because mobile WiMAX is able to handle wide range mobility. That is not true, however; in the previous sections we have seen that there are a lot of differences between a WiMAX system and a 4G system. Regardless, the impact of 4G is quite encouraging for all the mobile research community. Not only will the 3G GSM core network be evolved, but it would also be a tremendous system with a lot of advanced features for the future and capable of successfully handling the increased need.

The biggest impact will be on the business community, which is spending a huge amount for the 4G research in the hopes of receiving a good return. There is no doubt that 4G can generate a huge amount of revenue, but the timeline and other socio-political issues like spectrum distribution and health effects are making things complex. 4G would change the communication scenario to a large extent. Broadband services in the wireless mode would be appreciated by a large number of customers. Video transfer through wireless IP would be revolutionized.

Another interesting scenario for the 4G systems would be in the mobile computing arena. The 4G handsets would be nothing but some kind of advanced palmtops with broadband connection, so we can imagine what is going to happen and what kind of service can be expected. Business will go really mobile. That means that the true m-commerce would come to the market and true ubiquitous computing could be realized. Of course, the overall effects of 4G are now just predictions whose realities will only be witnessed in the future

ARCHITECTURE OF 4G

At this moment it is very difficult to predict the exact architecture of the 4G mobile communication system. Looking at the present scenario of the 3G and the likes of WiMAX etc. we can only predict the probable architecture of the fourth generation architecture. However in labs and on an experimental basis there are already some of the architectures available for the 4G. Of course, with the advances of the technology in both the UMTS and the CDMA 2000 and their evolved versions the architectures will be updated. Here some of the experimental architectures and some of the predicted models of the 4G architecture have been presented.

1. The OSI Model for 4G

The best way to represent any communication system architecture is the OSI model, and here the probable OSI model of 4G model has been presented (Figure 1) with the understanding that may be some differences in specific future 4G systems. The OSI model of 4G can properly explain the different operations of and the underlying technologies. It is similar to the various layers found in the OSI model of internet, but as a result of basic differences they are arranged in a different fashion and some of the layers are absent. Here the physical layer and the MAC (medium access control sublayer) are quite important.

 

Figure 1: The OSI model of4G

The OSI model of 4G depicts the different layers and their functions in a proper sequence. The physical layer, or bottom one, deals with the signals in the OFDM format. Above it lies the transmission convergence sublayer (CS), which is between the physical layer and MAC layer. On top of that layer is the MAC layer, which has three sublayers. The uppermost layer of MAC, the convergence sublayer, supports both ATM services as well as IP based services. In 4G the MAC layer at the base station (BS) is responsible for the allocation of bandwidths to different users both in the uplink and downlink. MS only occasionally takes the control of bandwidth allocations when it has multiple sessions or it has connections with the BS. This is quite different from other services and ensures better quality of service. Most of the services of 4G would be IP based; as a result the optimization and QoS related improvements are done as per the IPv6 configuration and structure. ATM service facilities are also provided for the compatibility with other existing networks.

When we look at the first release of WiMAX standard in 2001, the IEEE 802.16 standard proposed applications for a fixed wireless scenario in licensed frequency bands in the range between 10 and 66 GHz, where the use of directional antennas were mandatory to obtain satisfactory performance figures. But difficulties were encountered in metropolitan sub-areas where line-of-sight operations cannot be ensured due to the presence of obstacles, buildings, towers etc. Thus, subsequent amendments to the standard (IEEE 802.16a and IEEE 802.16-2004) have extended the 802.16 air interface to non-line-of-sight applications in licensed and unlicensed bands in the 2-11 GHz frequency range. Additionally, after the revision of IEEE standard document 802.16e, some necessary mobility support will be provided. Revision of IEEE 802.16f is intended to improve multi-hop functionality, and 802.16g is supposed to deal with efficient handover and improved QoS. This revision also increased the range of WiMAX technology; according the WiMAX forum, it can reach up to a theoretical 50 Km coverage radius and achieve data rates up to 75 Mb/s. Of course, actual IEEE 802.16 equipment is still far from these performance figures, but it has been proved that with the use of MIMO antennas and OFDM based technologies the data rates can be made really high. For example, with 5 MHz bandwidth, a data rate of 18 MBPS is possible using this advanced MIMO technique. After looking at the success of these technologies in WiMAX, the 4G development research groups are ready to follow the same path. Most of the settings of 4G would be according to the IEEE 802.16m standards, and the new MAC layer bridging is waiting for some amendments of IEEE 802.16k.

Duplexing or bidirectional data transmission is provided by means of either Time Division Duplexing (TDD) or Frequency Division Duplexing (FDD). In TDD, the frame is divided into two sub-frames, one devoted to downlink and the other to the uplink. A Time-Division Multiple Access (TDMA) technique is used in the uplink subframe. The BS is in charge of assigning bandwidth to the SSs, while a Time Division Multiplexing (TDM) mechanism is employed in the downlink sub-frame. In case of FDD, the uplink and downlink sub-frames are concurrent in time, but are transmitted on separate carrier frequencies. There are supports for half-duplex FDD SSs, at the expense of some additional complexity. Each subframe is divided into physical slots. Each TDM/TDMA burst carries MAC Protocol Data Units (PDUs) containing data towards SSs or BS, respectively. The transmission convergence sublayer operates on top of the physical layer and provides the necessary interface with the MAC. This layer is specifically responsible for the transformation of variable length MAC PDUs into fixed length physical blocks. Here in 4G, the RR and the MM layers are different from the GSM RR and MM layers. Here the use of MIMO enabled antennas can manage the resources quite efficiently.

There is a big demand for secure data transmissions, which has led to the native inclusion of a privacy sub-layer in 4G (which is very similar to the WiMAX), at the MAC level. There are some well-organized protocols to take care of the security related processes. Those protocols are responsible for encryption/decryption of the packet payload, according to the rules defined in the standard. IEEE 802.16 uses a wireless medium for communications, and one of its main targets of the MAC layer is to manage the resources of the radio interface in an efficient way, while ensuring that the QoS levels negotiated in the connection setup phase are fulfilled. Of course the IEEE 802.16 MAC protocol is connection-oriented and is based on a centralized architecture. There is a need for segmentation and resemblance of frames for proper security monitoring of all the packets. The common part sublayer is responsible for this segmentation and the resemblance of MAC service data units (SDUs), the scheduling and the retransmission of MAC PDUs. The common part sublayer also provides the basic MAC rules and signaling mechanisms for different system access, bandwidth allocation and connection maintenance. The core function of the protocol is bandwidth requests/grants management. A SS may request more bandwidth, by means of a MAC message, to indicate to the BS that it needs (additional) up-stream bandwidth. The request of bandwidth is processed on a per-connection basis to allow the BS uplink scheduling algorithm, to consider QoS-related issues in the bandwidth assignment process. The bandwidth granting methods as per the original 2001 standard encompassed two operational modes: Grant per Connection (GPC) and Grant per Subscriber Station (GPSS). Later in the 2004 release, the term "grant" refers only to the GPSS mode. Whereas, in the GPC mode, the BS allocates different scalable bandwidths to individual destinations. With this revision, BS got the control of all the centralized mechanisms, with all the intelligence placed in the BS, while the SSs act as merely passive stations. On the other hand the bandwidth, in the GPSS mode, is granted to each individual SS, which is then in charge of allocating the available resources to the currently active flows.

Convergence sublayer (CS) is the uppermost sublayer of the MAC layer. The CS associates the traffic coming from the upper layer with an appropriate Service Flow (SF) and Connection Identifier (CID) which gives the idea about its destination. The CS also provides payload header suppression when some entity is sent and reconstruction at the receiving entity. CS delivers the resulting CS PDU to the MAC Common Part Sublayer to confirm the negotiated QoS levels.

The 4G standard defines two different Convergence Sublayers for mapping services to and from IEEE 802.16 MAC protocol like the WiMAX. The ATM convergence sublayer is there solely for ATM traffic, while the packet convergence sublayer is specific for mapping packet-oriented protocol suites, such as IPv4, IPv6, Ethernet and Virtual LAN etc. The IP Sublayer is as the name suggests is there to provide all IP enabled services. The classification of IP traffic and ATM traffic is done in the CS sublayer. However the system's IP architecture will be based completely on IPv6.