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In this review we have discussed the 4G (forth generation) communication system and the wireless sensor network in the 4G communication system. For this purpose, we collected information from books and some research journals, about what 4G is why 4G is required and we have also compared 4G with previous generation of communication systems such as 1G,2G,3G. We discussed that the 4G communication systems are much more efficient it terms of bandwidth, speed and the number of users to facilitate. We have also discussed the basic technologies for the 4G networks. we have in detail explore the wireless sensor networks and explained the basic sensor networks their basic design, characteristics ,architecture, routing protocols and the functionality of the wireless sensor networks. We have also briefly explained the advantages of the 4G (fourth generation) communication systems. In the end we have given a brief conclusion based on our own observation
The fourth generation communication system and its comparison to previous generation systems
1.1 What is 4G?
4G (fourth generation) technology is the next generation of wireless networks that will replace the 3G (third generation) networks in the future.
it is capable of providing IP solution to the user where data ,voice and multimedia can be provided on anytime ,any place basis.
it is a full IP based integrated system having higher data rates than the previous technologies ranging from 100 M bit/s to 1Gbits/s.It also allows a premium quality and a high Security data transmission.
1.2 Why 4G?
3G is necessary but not sufficient to the mobile communication strategy, in which many problems are only partly solved and there are still many problems left to be
Solved in the next generation.4G communication system is required because 3G system has some shortcomings given as follows:
- 3G performances are not sufficient to meet the future high-performance application like multimedia, video and wireless teleconferencing, so a network having extended capacity than 3G is desired.
- There are multiple standards for 3G that makes it difficult to operate across networks. We need global mobility and service portability.
- 3G is based on wide area concept but networks are required that use both the LAN and wide area network concept.
- More bandwidth is required.
- Researchers have come up with new modulation techniques that can not be implemented in the 3G systems.
- Networks are required that utilizes IP in its fullest with converged voice and data capability .
- Limitation of spectrum and its allocation.
- Lack of end-to-end seamless transport mechanisms .
1.3 Comparison with previous generation’s communication systems:
1.3.1 1G (first generation) communication systems:
The first generation communication system is based on analog data communication .signal that is continuous in amplitude and time is used as the source of communication.
It used the simplest type of wireless data and its average speed ranges from 4,800 to 9,600 bps (bits per second).
1.3.2 2G (second generation) communication systems:
The second generation communication system uses the digital data consisting of 1,s and 0,s .Digital data can be compressed and multiplexed much more easily than the analog data used in the first generation communication systems. CODEC was introduces in the 2G communication systems. It is a program that encodes and decodes digital data streams and signals. Multiplexing such as FDMA (frequency division multiplexing access), TDMA (time division multiplexing access), and CDMA (code division multiplexing access) was efficiently used in this generation. There are certain advantages and disadvantages of this generation communication system given as
- The digital voice encoding allows digital error checking.
- Sound quality is better than the 1G communication systems
- Lowers noise level than the 1G communication system.
- Services like SMS (short message service) and E-mail was introduced.
- Limited coverage area.
- Analog has a smooth decay curve, digital a jagged steep one. Under good conditions, digital will sound better. Under slightly worse conditions, analog will experience static, while digital has occasional dropouts. As conditions worsen, though, digital will start to completely fail, by dropping calls or being unintelligible, while analog slowly gets worse, generally holding a call longer and allowing at least a few words to get through.
- With analog systems it was possible to have two or more "cloned" handsets that had the same phone number. So it can be used for illegal purposes. It was, however, of great advantage in many legitimate situations. One could have a backup handset in case of damage or loss, a permanently installed handset in a car or remote workshop, and so on. With digital systems, this is no longer possible.
- While digital calls tend to be free of noise, the use of CODEC takes a toll; the range of sound that they convey is reduced. You'll hear less of the tonality of someone's voice talking on a digital cell phone, but you will hear it more clearly
1.3.3 3G (third generation) communication systems:
3G the third generation of communication systems introduced large capacity and broad band capabilities. It allows the transmission of 384kbps and up to 2Mbps.it has increased spectral density about 5Mhz.In 3G systems a greater number of users can be simultaneously supported by a radio frequency bandwidth .The basic comparison between the 3G and the 4G communication systems is given as
3G (third generation )communication systems
4G(fourth generation ) communication systems
It is predominantly voice driven
Converged voice and data over IP
It uses wide-area cell based network architecture
It uses hybrid architecture including both the wireless LAN and the wide area networks.
It can provide speed ranging from 384Kbps to 2 Mbps
It speed limit ranges from 20 Mbps to 100 Mbps
Frequency band ranging from1800 MHz to 2400 MHz
High frequency band from 2-8GHz.
Bandwidth from 5-20 MHz
Higher bandwidths up to 100 MHz and more.
Switching design is based on circuit and packets
Switching design is all digital with packetized voice.
Access technologies used are W-CDMA, 1xRTT, Edge.
Technologies used are OFDM and MC-CDMA(multiple carrier CDMA).
1.4 How 4G works:
The basic technologies used in the fourth generation systems are
- Ad Hoc networking
- Mobile Ipv6
- Mobile VoIP
1.4.1 OFDM (orthogonal frequency division multiplexing):
This type of multiplexing allows transfer of more data than other types of multiplexing such as FDMA (frequency division multiplexing access), TDMA (time division multiplexing access) and CDMA (code division multiplexing access) used in previous generation systems. It has also simplified the design of transmitter and receiver .
1.4.2 Ad hoc networking:
It is spontaneous self organizations of networks of devices. Hybrid wireless network are created using these networks. This type of networking is quiet similar to mesh networking and is very reliable .
1.4.3 Mobile IPv6:
The 4G communication system is an IP based communication system. The mobile IPv6 allows each device to have own IP. It will keep the address even if you change access point. It also translates IP with each change because not enough IP addresses to go around.
1.4.4 Mobile VoIP:
Mobile VoIP is termed as the ‘Voice over Internet Protocol’. It allows only packet (IP) to be transmitted eliminating the complexity of two protocols over same circuit. It samples voice between 8,000 and 64,000 times per second and creates streams of bits which is then compressed and put into a packet. It increases the battery life due to greater data compression .
The wireless sensors networks in the fourth generation (4G) communication systems
2.1 Sensor Networks:
Sensor networks have attracted a lot of attention lately. These wireless networks consist of highly distributed nodes with energy and resource constraints. Driven by advances in micro electromechanical system (MEMS) micro sensors, wireless networking, and embedded processing, ad hoc networks of sensors are becoming increasingly available for commercial and military applications such as environmental monitoring (e.g., traffic, habitat, security), industrial sensing and diagnostics (e.g., factory, appliances), critical infrastructure protection (e.g., power grids, water distribution, waste disposal), and situational awareness for battlefield applications. sensor networks offer a rich source of problems that include sensor tasking and control, tracking and localization, probabilistic reasoning, sensor data fusion, distributed databases, and communication protocols and theory that address network coverage, connectivity, and capacity, as well as system/software architecture and design methodologies.
2.2 A Typical Wireless Sensor Network:
A typical wireless sensor network consists of a number of sensor nodes and a control center. To perform a detection function, each sensor node collects observation data from the surrounding environment, does some processing locally if needed, and then routes the processed data to the control center. The control center is responsible for making a final decision based on all the data it receives from the sensor nodes .
2.2.1 Basic design:
A wireless sensor network as a large-scale (thousands of nodes, covering large geographical areas), wireless, ad hoc, multi-hop, un partitioned network of homogeneous, tiny, mostly immobile sensor nodes that would be randomly deployed in the place of interest. The network design can be varied on the actual needs of the application, the form factor of a single sensor node may vary from the size of a shoe box to a microscopically small particle (e.g., for military applications where sensor nodes should be almost invisible). Similarly, the cost of a single device may vary from hundreds of Euros (for networks of very few, but powerful nodes) to a few cents (for large-scale networks made up of very simple nodes).
Early sensor network visions anticipated that sensor networks would typically consist of homogeneous devices that were mostly identical from a hardware and software point
of view. It was even assumed that sensor nodes were indistinguishable, that is, they did not even possess unique addresses or IDs within their hardware. However, in many prototypical systems available today sensor networks consist of a variety of different devices. Nodes may differ in the type and number of attached sensors; some computationally more powerful “compute” nodes may collect, process, and route sensory data from many more limited sensing nodes; some sensor nodes may be equipped with special hardware such as a GPS receiver to act as beacons for other nodes to infer their location; some nodes may act as gateways to long-range data communication networks such as GSM networks, satellite networks, and many more .
2.2.2 Network characteristics:
The management of sensor networks is a non trivial task. Recent research on the management of the wireless sensor networks has mainly focused on topology and connectivity. Network management is a process to control a complex network to increase its efficiency and productivity. It is very important to manage a sensor network. Especially most wireless sensor nodes are powered by battery rather than external power so the energy conservation is a key issue for the design and implementation of a sensor networks. Effective management of a sensor network requires a practical architecture that is optimized to the features of wireless sensor networks and satisfies the requirement of the management protocol. The architecture of a sensor network has three characteristics:
- Scalability. Sensor networks rely on thousand of tiny sensors, these sensors do not necessarily to be active all the time so sensors can be dynamically added or removed form the network. The scalability factor allows response to change in sensor states.
- Task orientation. The task of the sensor networks range from the simplest data capturing and static nodes to the most difficult data collecting, mobile-node sensor network. The software structure is reasonably optimized and tailored according to the pre-defined task-set of each node.
- Light weighting. Lightweight operations such as aggregation, reduced message size and piggyback acknowledgment mechanism can be easily applied to the system due to light weightiness .
2.3 Management architecture:
Wireless sensor networks share several familiar features with the general mobile wireless ad hoc networks; they have their own differences for example a sensor node has a small fixed processor with more limited memory and energy than a general ad-hoc node also The wireless sensor network intrinsically has at least one base station, which is the most possible candidate for the manager. The communications with internet devices are generally implemented via the base station, due to the reason of the base station and advantages of hierarchy architecture that is effective for data aggregation (light weighting) and scalability therefore the wireless sensor network's management architecture should be centralized and hierarchical.
2.3.1 Basic Architecture:
WSN networks basic architecture is divided into three layers. The highest layer is the manager node in the base station. The middle layer is a cluster head locating the master agent. The lowest level is other left over nodes, locating slave agents. The master agent is answerable for communication between slave agents in its clusters and the manager, while the slave agent is responsible for reporting the MIB data of its own node to the master agent. The basic architecture has following main features
- The manager is determined by the base station. The number of base stations equals to the number of managers, although the number of managers could be smaller. If there is only one manager, the architecture is centralized. If there are two managers or more, the architecture can be centralized or distributed.
- Every sensor cluster has only one sensor node as master agent at a time.
- One separate node is an independent cluster and becomes the cluster head automatically.
2.3.2 Clustering Algorithm:
The core of a hierarchical architecture is the clustering algorithm. Two clustering algorithms are purposed:
Graph-based Clustering and Geographical-based Clustering. Geographical-based clustering is not suitable for wireless sensor networks for the prohibitive Global Positioning System (GPS). Graph-based Clustering effectively reduces communication traffic, but it omits the task-oriented feature. Besides, it's a complete distributed algorithm without taking into consideration of the central base of wireless sensor networks. To avoid these effects another clustering algorithm is used having the following properties
- Each sensor node has a unique ID.
- Each sensor node holds its one-hop neighbor list.
- Each sensor node in one sensor network runs a specific task including one or more data to form a task data pattern.
2.3.3 Maintaining cluster:
The sample value of a node changes with time. Although the pattern value is usually restricted within original data area range, sometimes it goes beyond the range. Once the master agent detects such difference after enough times, the new pattern is reported to manager, such sensor node is recomputed to more suitable area. This node can unite one cluster according its neighbor lists, and become an independent cluster otherwise. Three update messages will be sent from manager to the original cluster head, the new cluster head and the updated node separately. Topology changes take place when a node moves out of a cluster or the cluster head itself move away from the cluster therefore cluster is reformed according to neighbor list.
2.3.4 Data aggregation:
Data aggregation is an important way to attain light weighting and energy preservation. It takes place in master agent and is the strong point of the task-oriented clustering algorithm .It allows high compression rates and operation simplicity .
2.4 Routing in sensor networks:
In sensor networks, up-to-date, less effort has been given to routing protocols, even though it is clear that ad hoc routing protocols (such as destination sequenceddistancevector (DSDV), temporally-ordered routing algorithm(TORA), dynamic source routing
(DSR), and ad hoc on-demand distance vector(AODV) are not suited well for sensor networks since the main type of traffic in WSNs is “many to one” because all nodes typically report to a single base station or fusion center. Nonetheless, some merits of these protocols relate to the features of sensor networks, like multi hop communication And QoS routing. Routing may be associated with data compression to enhance the scalability of the network .
2.4.1 Routing protocols:
There are many ways to classify the routing protocols for the sensor networks such as flat hierarchical according to the network structure. Further these protocols are classified as multi path based, query based, negotiation based, and quality of service (QoS) or coherent based. Some of the routing protocols are given below
Flooding is an old technique that is also used in sensor networks. in flooding each node received a data then sent them to the neighbors by broadcasting ,unless a maximum number of hops for the packet are reached or the destination of the packet is arrived.
184.108.40.206 Spin (sensor protocol for information via negotiation):
It is used to pursue a data centric routing mechanism. The idea behind SPIN is to name the data using meta-data that highly describes the characteristics of the data which is a key feature of SPIN.
SPIN has three types of messages
- ADV- when a node has data to send, it advertises this message containing Meta data.
- REQ-A node sends this message when it wishes to receive the data.
- DATA-Data message contain the data.
220.127.116.11 LEACH (low energy adaptive clustering hierarchy):
It is a clustered based protocol that utilizes randomized rotation of the cluster heads to evenly distribute the energy load among the sensor nodes in the network. It is one of the most important sensor networks protocol. The idea is to form the clusters of the sensors nodes based on the received signal strength and use local cluster heads as router to the sink. This will save energy since the transmission will only be done by cluster heads rather than all the nodes.
18.104.22.168 GEAR (Geographic and Energy Aware routing):
It uses energy aware and geographically informed neighbor selection to route a packet toward the target region. Each node keeps an estimated cost and a learning cost of reaching the destination through its neighbors. There are two phases in the algorithm: one is the forwarding the packets toward the targeted region and other is the forward packets within the region. Compared to GPSR, which is one of the earlier protocols in geographic routing, GEAR not only reduces energy consumption for the route set up, but also performs better than GPRS in terms of packet delivery.
2.5 Network functionality:
Wireless sensor network functionality consists of processes like configuration, sensing processing, communication and maintenance.
This functionality involves procedures related to planning, placement and self organization of WSN. WSNs can be classified in various ways. A WSN is said to be homogeneous when all nodes have the same hard ware otherwise I is said to be heterogeneous. A WSN is hierarchical when nodes are placed for the purpose of communication and is otherwise flat. Considering the network element management level and management functional areas are based on the configuration functionality, the sensor in a WSN is spread over a region and communicates among them using point –to –point wireless communication. Software developed to execute in a wireless
Sensor node must take into account its hardware restrictions. WSN comprises three entities: observer, phenomenon, and environment. The observer is a network entity or a final user that wants to have information about data collected, processed, and disseminated by sensor nodes. Depending on the type of application, the observer may send a query to the WSN, and receive a response from it. These queries can be done with or without fidelity. The translation of the query could be performed by the application software or sensor nodes
Sensing is provided by the autonomous sensor nodes. An important operation in sensor network is gathering data .WSNs can be divided in terms of gathering data as continuous(when nodes collect data continuously along the time) , reactive(when they answer to observers query and gather data) and periodic(when nodes collect s data according to conditions defined by the application).these approaches can also coexist in same networks.
Processor for a sensor node forms a computational module. This is a programmable unit that can provide computation and storage for other nodes in the system. Depending on the communication constraints of the system, algorithms must be developed that will allow individual nodes or clusters of nodes to share and process data efficiently. The computational module performs basic signal processing and dispatches the data according to the application. Processing involves correlation procedures such as data fusion, which combines one or more data packets received from different sensors to produce a single packet (data fusion). Data fusion helps to reduce the amount of data transmitted between the sensor nodes and the observer and allows design of a network that delivers required data while meeting energy requirements. Other possible tasks are security processing and data compression.
Individual nodes communicate among themselves. Two types of communication are suggested: infrastructure and application. Infrastructure communication refers to the communication needed to configure, maintain, and optimize operation. The configuration and topology of the sensor network may be rapidly changing in the presence of a unfriendly environment, a large volume of assigned work, and nodes that fail regularly. Conventional protocols may be insufficient to manage such situations; thus, new protocols are required to promote WSN productivity. In a static sensor network, an initial phase of the infrastructure communication is needed to set up the network and an additional communication is needed to carry out its reconfiguration. The amount of energy used up in transmitting a packet has a fixed cost related to the hardware and a variable cost that depends on the space of transmission. Receiving a data packet also has a set energy cost. Therefore, to conserve energy, short distance transmissions are favored. In terms of the data delivery required by the application importance, WSNs can be classified as continuous, when sensor nodes gather data and send them to an observer continuously along the time, and as on order, when they answer an observer’s query. A WSN is event driven when sensor nodes send data referring to events occurring in the environment and programmed when nodes collect data according to situation defined by the application.
Multi hop wireless capabilities will enable communication and coordination among autonomous nodes in unplanned environments and configurations. The communication approach can be classified as:
• Flooding (sensors spreading their information to their neighbors, which in turn broadcast these data until they reach the observer)
• Gossiping (sending data to one arbitrarily selected neighbor)
• Bargaining (sending data to sensor nodes only if they are concerned)
• Unicast (sensor communicate to the sink node, cluster head, or BS directly)
• Multicast (sensors forming application-directed groups and using multicast to communicate among group members)
Maintenance is used in the WSNs that can organize, defend, optimize and heal themselves without a lot of input from the human operators who have, until now, been required to keep traditional networks running. Maintenance detects failures or performance degradations, initiates diagnostic procedures, and carries out curative actions on the network. Its skill to discover changes in the network state enables the self-management to adapt and optimize the network.
The impact of 4G (fourth generation) communication systems
3.1 Advantages of 4G:
Fourth generation (4G) communication systems provides bandwidth efficiency and low complexity receivers to accommodate high data rates and large number of users. The forth generation communication systems are much more efficient than the previous generation systems. Some advantages of the 4G communication systems are given below
- More affordable communication services
- One device can communicate with all similarly many devices communicating with some devices.
- TV, internet, phone, radio, home environment sensors all reachable through one device.
- Increase in social networking, invasion of privacy, and security concerns .
- Greatly increased the spectrum efficiency.
- Mostly ensure the highest data-rate to the wireless
- Best share the network resources and channel terminal utilization
- Optimally manage the service quality and multimedia applications .
- As 4G is IP based and IP is compatible with, and independent of, the actual radio access technology.
- A 4G network is cheaper than a 3G network.
- Improved data access for mobile Internet devices
- A 4G communication system is much faster than the previous generation systems.
The ever-increasing growth of user demand, the limitations of the third generation of wireless mobile communication systems and the emergence of new mobile broadband technologies on the market have brought researchers and industries to a thorough reflection on the fourth generation. Many prophetic visions have appeared in the literature presenting 4G as the ultimate boundary of wireless mobile communication without any limit to its potential. A 4G communication system is much more efficient in term of speed, bandwidth and the number of users to facilitate. The basic technologies used in the 4G systems are by far better than the previous generation systems such as OFDM and Ad-Hoc networks, wireless networking, and embedded processing. Networks of sensors are becoming increasingly available for commercial and military applications such as environmental monitoring, industrial sensing and diagnostics, critical infrastructure protection, and situational awareness for battlefield applications. sensor networks offer a rich source of problems that include sensor tasking and control, tracking and localization, probabilistic reasoning, sensor data fusion, distributed databases, and communication protocols and theory that address network coverage, connectivity, and capacity, as well as system/software architecture and design methodologies.
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