CHAPTER 3 4G NETWORK ARCHITECTURE

Transcription

1 62 CHAPTER 3 4G NETWORK ARCHITECTURE Wireless mobile communication system generations are all the time, a big topic for the research. Cellular service providers are already in the last phase of the deployment of 3G in the major parts of the world to achieve higher data rates. 3.14G WIRELESS SYSTEM FEATURES The 4G technology includes all types of advanced features that make 4G technology, the most dominant technology in the near future. 1. It should provide support to wireless elastic multimedia, video, audio, wireless Internet, and other broadband services. 2. It should support for worldwide roaming or service and device portability, and increased mobile networks. 3. It must be capable enough to provide high capacity, increased speed, and a minimized cost per bit data rate. 4. It should provide seamless packet switching, and other services based on the requirement of the quality of service. 5. It should have good scheduling techniques, and also call admission control schemes. 6. It should also support for ad hoc and multi-hop networks. 4G and 5G systems have two types of networks: 1) Cellular Mobile WiMAX and 2) LTE-Long Term Evolution. To provide

2 63 accommodations the increased need for cellular and multimedia applications, 3GPP established LTE-Long Term Evolution mobile networks (Amit Kumar et al 2011). To exchange multimedia pictures and live audiovisual streams from the network, the organization requires wireless data sending abilities. But these requirements can t be achieved by the existing narrowband schemes. This leads to the improvement of new mechanisms such as LTE- Long Term Evolution, which provides the transmission of high-end video streams (J. Brouet et al 2011) Comparison between 3G and 4G systems The following table 3.1 shows a comparison among the 3G and the 4G wireless mobile systems under some parameters. TABLE 3.1: The comparison between 3G and 4G Sr. No. Constraints 3G 4G 1 Frequency range GHz 2-8GHz 2 Bandwidth 5-20MHz 5-20MHz 3 Data speeds Upto 2 Mbps and 384 Kbps for WAN Upto 1Gbps 4 Access Technology Wideband CDMA OFDMA using TDMA or Multicarrier- CDMA 5 FEC Turbo codes Connected codes 6 Switching Packet or circuit switching Only Packet switching 7 Mobile top speeds 200 Kmph 200 Kmph

3 G Network Structure Fig3.1 is a widely accepted IP Based 4G network architecture that is used for wired/wireless communication accommodating 2G, 2.5G, 3G, & 4G convergence technologies (A.H Khan et al 2009). Fig3.1. 4G Network structure Fig3.2 shows the protocol stack architecture of 4G networks (B. Liu et al 2013). This protocol stack fulfills the very basic need of serving the fixed and cellular mobile users on an anytime, anywhere & anyhow, in dynamic network conditions. This protocol stack uses the IPV6-Internet protocol version 6. In heterogeneous networks, it operates at the transport layer. It is based on

4 65 the mobility, QoS, & efficient resource allocation techniques. Here, we explain the services of each layer & module (Piyush Gupta et al): Fig.3.2:4G protocol stack architecture 1. Application layer: This layer provides value added services as a third party application to its subscriber. 2. Network layer: This layer contains a number of sub layers as described below: a. Services: This layer is responsible for the interaction among the various value added services and network systems. b. Mobility Management: This layer is responsible for continuous services to the mobile wireless devices in heterogeneous systems. To optimize handoff latency and

5 66 packet loss to the last subscriber moving through heterogeneous network systems, it updates the care of the address of the mobile user called binding update and location management. It also performs Common Control Signaling for address assignment, network discovery, and handoff control techniques. c. Resource Management: This layer is responsible for the resource allocation, and reallocation that are acquired while moving from one network to another network. This resource allocation, de-allocation, or reallocation can be done before or during the communication activity. This layer also does the packet scheduling, packet analysis, congestion control, & classification. d. Quality of Service Provisioning: The optimized utilization of the available resources is done in this layer. It also gives an option to select between end to end delay & throughput to the application user. 3. Physical layer: The core IPV6-Internet Protocol Version 6 network of 4 th Generation & other dissimilar access networks such as CDMA, GSM, & WLAN are the parts of this layer. This layer is divided into two sub-layers as described below: a. Convergence layer: At the physical level, the convergence layer gives the CCS-Common Control Signaling mechanism between the core and dissimilar wireless systems. E.g. resource management, mobility management, and QoS management.

6 67 b. Radio Access Networks (RAN): RAN at the physical level, contains many radio access network systems that are communicating among them. 4. Administration, Operation, Maintenance, & Provisioning: This network layer provides the network system monitoring, controlling, fault detection, & resource management of the various heterogeneous & basic networks, which is present in all the layers. 5. The security layer: This layer is also present in entire protocol layers. This layer performs different kinds of security services such as the Authorization, Encryption, Authentication, Decryption, the Establishment and Implementation of the service policy agreement among the various operators. 3.2 WIMAX SYSTEM ARCHITECTURE In mobile wireless communication network systems, wireless broad-band WiMAX systems as shown in fig3.3 are major technologies in the near future. The Mobile IP allows data handover over the dissimilar sub network systems. The next generation internet protocol uses IPV6 for future networks. The world is moving towards a convergence of data, voice, and audio-video applications. This heterogeneity will expect inter-operability, and a very large data rate. So, the IEEE 802 working group has formed the working committee in 1999, to design mobile wireless broadband technology. The WiMAX offers wireless data transmission with the help of different transmission types such as portable, point to multi-point links, and fully mobile internet data access. This technology offers up to 10 Mbps bandwidth

7 68 without cables. The technology is set up to provide low-cost access having pervasive broadband call admission with combined data, and multimedia and non-multimedia services. The most important benefit of wireless broadband mechanism is that the mobile communication systems may be created in two to three days by forming a few base stations at the buildings to develop large capacity mobile cellular access networks. The wireless cellular systems may grow as the need increases. Fig 3.3: WIMAX Architecture. The IEEE controls the air-interface and the associated tasks related with WLL-Wireless Local Loop. Three operational groups have been set up to develop the following technology: 1. The IEEE The air interface for 10GHz - 66 GHz. 2. The IEEE The coexistence of broadband cellular wireless access networks.

8 69 3. The IEEE The air interface permitted licensed frequencies 2GHz- 11 GHz. 4. The broad radio band is accessible in the frequency range of 10 GHz -66 GHz globally. In the commercial development, can serve as a backbone support for networks. The IEEE technologies are associated with the air interface amongst a subscriber s transmitter and receiver station and the base transmitter and receiver station. The standards are arranged into a three layer-wise architecture as shown in the figure The physical layer: This layer states the frequency band, modulation schemes, synchronization among data rates, error correction techniques, trans-receiver, and the multiplexing technology. The WiMAX network supports a number of transmission types at the physical level such as SC-Single Carrier type, and the OFDM & OFDMA types. In the OFDM network systems, the FEC-Forward Error Correction coding technique is used to reduce the rate of error in the transmitted data stream. Reed Solomon Concatenated with a convolution code is compulsory for all WiMAX networks. The final data block is categorized into various parallel low-speed data blocks, and mapped to an individual data sub-carrier. Then, it is modulated with the help of either PSK-Phase Shift Keying or QAM- Quadrature Amplitude Modulation such as BPSK-Binary Phase Shift Keying, QPSK-Quadrature Phase Shift Keying, 16QAM-16 Quadrature Amplitude Modulation, and 64QAM-64 Quadrature

9 70 Amplitude Modulation. Hence, the modulation is the procedure for translating the data blocks into a proper transmission form over the physical medium. Modulation, Demodulation and coding rate combinations of WiMAX and OFDMA are shown in Table 3.2. Table 3.2: The modulation and coding rate combinations of WiMAX and OFDMA (Source wireless network 2011). Modulation rate for overall coding code rate for CC code rate for RS QPSK ½ 2/3 (24,18,3) QPSK ¾ 5/6 (30,26,2) 16QAM ½ 2/3 (48,36,6) 16QAM ¾ 5/6 (60,52,3) 64QAM 2/3 ¾ (81,72,4) 64QAM ¾ 5/6 (90,82,4) 2. The MAC-Medium Access Control layer: The function of MAC layer is for the transmission of data in packet frames, and it regulates the access to a shared wireless air medium through medium access control layers. The MAC layer protocol describes how and when a base transmitter receiver or a mobile subscriber station can start communication on the available channel. 3. Convergence layer: Above the MAC layer, this convergence layer offers tasks specific to the services given to the upper layers.

10 71 The IEEE bearer service consists of digital telephone system, Asynchronous Transfer Mode, digital audio and video multicast, telephone networks, Internet access, and wireless voice calls in frame relay systems. a. A subscriber transmits wireless cellular traffic at a speed going from 2 Mbps-155 Mbps in a fixed antenna systems on a building. b. The base station gets communications from several sites, and pushes this traffic through wireless or wired links to a packet switching center with the help of the standard c. The switching center pushes the traffic to an ISP-Internet Service Provider, or the PSTN-Public Switched Telephone Network. In the MAC layer of the WiMAX, the resource distribution is dynamically accomplished by the base station. The WiMAX network can control the modulation and coding scheme (MCS) of each mobile wireless subscriber as per the wireless channel conditions to progress resource consumption. The base station collects the CQI-Channel Quality Indication of all the subscribers, and then, decides on an MCS-Modulation and Coding Schemes for each user using their own algorithms. This is very critical for improving the entire system performance of the WiMAX network. Hence, it is an important issue that how many free slots are allotted to each mobile user depending on the calculated MCS- modulation and coding scheme. This indicates

11 72 that the packet scheduling techniques and call admission control schemes are required to enhance the QoS of NGN networks. 3.3 CALL ADMISSION CONTROL In the next generation mobile wireless network, CAC is taken as one of the RRM- Radio Resource Management issue, which has a direct impression on the QoS for an individual RT & NRT calls, and whole system performance (Reza Malekian et al 2013, H. A. M. Ramli et al 2009). For CAC, the RRM mechanism is very crucial for QoS provisioning in the mobile wireless cellular systems. The key idea of CAC-Call Admission Control, is to ensure the QoS of individual calls by neatly, managing the network resources. The important characteristics that the call admission control policy has to provide are as follows: 1. Create a robust priority allocating schemes for handoff requests and RT, and NRT requests. 2. Design a low CBP-Call Blocking Probability. 3. Allocation of resources equally. 4. Achieving a high network throughput. 5. Avoid congestion. The call admission control algorithm should not violate the SLAs of the ongoing calls during the admission of new calls. The call admission control decision should be taken by considering multiple parameters such as the network characteristics, the service type, the user probability, and the network conditions (ITU-T , 2007). If the decision is taken positively, then the required resources should be

12 73 reserved and allocated to maintain the QoS of the new user. Thus, CAC is rigorously related to resource distribution, base station, channel assignment, resource reservation, and power control (J.J. Jaramillo et al 2011). The admission criteria applied in the decision making part of the CAC scheme could be: 1. Bit Error Rate (BER). 2. The call dropping probability (CDP). 3. The QoS at the connection level as determined by the data rate. 4. The delay bound, and the SIR-Signal to Interference Ratio. The ratio of bit energy to the interfering density ratio (Eb/I0) & call blocking probability. In the design of the CAC scheme, the most common QoS-Quality of Service parameters for performance assessment are CBP-call blocking probability & CDP-call dropping probability (B. Liu et al 2013, F. Capozzi et al 2013). 1. The call blocking means avoiding fresh calls due to non-sufficient resources or frequencies in the cellular system, or not meeting the QoS requirement. 2. Call dropping means breaking of an current ongoing call during the handoff process. Call termination of an ongoing call is more annoying than blocking of a new call. That s why handoff calls are given greater priority than new calls in cellular wireless systems. We can either reserve an assured amount of bandwidth from the total available in a cellular system for handoff calls, or dynamically, assign channels for a specific call (ITU-T 1993).

13 74 A good CAC scheme for the next generation networks could be sufficient to provide a huge range of handoff rates. This inspires us to propose a new CAC-call admission control scheme, which is strong enough to provide a high range of handover rates for the next generation of wireless networks. In the proposed scheme, the main aim is to improve the call blocking probability (CBP) considerably, by keeping the call drop probability (CDP) constant over a large range of handoff rates. This motivates the application of the suggested method, for the next generation of mobile networks. The main objective of using the traditional CAC scheme based on channel reservation in the mobile networks is to decrease the CDP-call dropping probability. In the reservation CAC scheme, the part of the bandwidth is permanently reserved for handoff calls. Therefore, new calls are blocked in spite of reserved channels being available in the system for handoff purposes, but that are not used now. On the contrary, the newly initiated real-time high priority calls should be treated all together separately, to fulfill the high priority calls in the next generation of a wireless mobile network. Hence, we suggest the idea of channel borrowing for NRT calls, which carry non-delay sensitive data traffic. In our proposed scheme, the new NRT calls can use channels from the reserved channels of high priority handoff calls. After this allocation, if a handoff call arrives, and there is no free reserved channel exist in the cellular systems, it preempts the service of the borrower NRT calls. The preempted NRT calls are retained inside the queue & continue their service as soon as a channel becomes free (R. Malekian et al 2013). In this research work, our focus is on designing and performance study, and

14 75 the evaluation of the CAC reservation scheme, in, which we consider a Poisson arrival process for the handoff calls. 3.4 MULTIMEDIA SERVICES The Next Generation Network will provide convergence of all types of media over IP network such as voice, radio, audio-video, TV, and multimedia services. The Multimedia is a type of medium, which is formed with the help of more than one conventional medium. It is the mixture of text, images, audio, and animation video sent and manipulated by electronic means. The ICTs (Information and communication technologies) have expanded the scope of information of control and delivery. Through ICT it is now possible to let people experience at the same time, with more than one type of medium. When an individual is allowed to control multimedia delivery when, what, & how content is provide d, it is called interactive multimedia, e.g. Video game. When an end user is provided with inter and intra-linked multimedia information through, which he can navigate is called as hypermedia or non-linear multimedia. A piece of multimedia information is termed as linear if it has a predefined beginning, source, and end, which cannot be changed, for example, watching a movie. We know that to transmit the video of one second, we need 177 Mbps bandwidth, which is commonly not available. Hence, the audio-visual streaming service is suitable for the most significant applications of the multimedia service. The video data is suitable for the most major traffic

15 76 mechanisms over the cellular systems. Hence it is very difficult to transmit a large amount of video data over the low bandwidth mobile wireless network. The effective video compression algorithms are applied to advance the QoS of multimedia or video data, and to overcome the bandwidth limitation. The International standards such as MPEG-1-moving pictures expert group, MPEG-2 (ISO/IEC 1994), MPEG-4(ISO/IEC JTC 2001), AVC H.261 (ITU-T 1993), H.263 (ITU-T 1998), H.262 and H.264 (ITU-T 2007) have been developed to accommodate the different requirements of ISO/IEC and ITU-T respectively. In the internet, multimedia applications can be categorized into three major classes: 1. Streaming stereo-audio or video for example, a movie 2. Streaming live audio or video for example, a live cricket match 3. Real-time interactive audio or video, for example, video conferencing. For the time-sensitive multimedia application, timing consideration hold most importance. If the packets of any video-audio application, come across a delay of more than certain hundred milliseconds, they are essentially useless. The time-sensitive applications, such as online audio-video are to a good extent loss tolerant, for example, FTP data, web, Telnet, and file transfer applications. The elastic applications are extremely, sensitive to data loss, and for them, completeness and integrity of the data transferred are invaluably precious (Lyyapillai Ambika et al 2014).

16 PACKET SCHEDULING According to the ITU, the Next Generation Wireless Mobile Network is a packet based network, which can provide various telecommunication and data services. The NGN is also called the Beyond 3G (B3G) network. The B3G network architecture will be advanced to accommodate a broader range of mobile users, economic deployment, and applications. The NGN, also well-known as beyond 3G is to identify the next step in mobile wireless communications. Following are the features of the next generation wireless mobile networks: 1. The transition towards whole IP based Network structure. 2. The Support of mixed network technologies for example PSTN systems, Ad-hoc networks, LANS, WiMAX, and WiFi, etc. 3. The seamless handoff through both homogenous and dissimilar wireless access methodologies. 4. The Quality of Service support on the IP layer. 5. The use of a policy-based mechanism to evaluate QoS, the billing mechanism, and accounting for multimedia systems and services. 6. The secure admission to multimedia system services across the different networking environments. 7. The acceptance of multimedia system services in hybrid IPV6 or IPV4 based networks. 8. It will offer reliability, availability, security, and performance. 9. It accommodates more users per cell. 10. It supports for backward compatibility with the existing wireless standards.

17 78 The Mobile Internet Protocol agrees data handoff in the heterogeneous cellular network systems. The next generation internet protocol uses IPV6 for future networks to accommodate all the devices. The world is moving towards a convergence of data, voice, and audio-video applications to provide seamless service. This heterogeneity could observe inter-operability, and a very large data rate using high speed LTE and 5G technologies in the field of mobile cellular wireless network systems.