The Main Purpose For Using Communication Systems

Published Date: 02 Nov 2017

Security is far higher in a wired network, historically wireless has been a serious security flaw and only recently is WPA/2 deployed more widely to combat this inadequacy.\\Wireless is not essential for the internet infrastructure, it is not fundamental to the internet, it is the ease of accessibility it provides which is its fundamental benefit, with most wireless devices on the periphery of networks. When compared to wired communication, wireless communication has exposed its advantages for large distance communications include security and cost effective under some regulations.\\

\section{The OSI seven Layer Model}

In early stages of computer networking the development was slow and in a patented fashion. But after the formation of networking bodies together under the name of International Standards Organisations (ISO) and introduced open system interconnections (OSI) model. This model basically classifies the communication process into several steps which are small and securely defined in form of layers. The OSI seven layer model is also known as ISO seven layer model.1. Multi Hop wireless network:

The basic principle behind the introduction of WMNs is to improve the coverage range of conventional wireless networks with same channel capacity and also to provide connectivity among users which are in nonline-of-sight (NLOS). In order to achieve these requirements, mesh topology multi hopping can be more efficient which results in higher throughput.

2. Specifications need to fulfil:

The designed network should able to support Adhoc networking and also able to exhibit the properties such as self-healing, self-forming and self-organization within the network. Adhoc networking helps to achieve network performances includes easy placement, flexibility of network architecture, easy configuration, error acceptance and mesh connectivity.

3. Mobility dependents on topology of mesh nodes:

In general mesh routers are considered to be with minimum mobility whereas the clients being either in stationary or mobile nodes. Therefore in WMNs system, mobility differs from node to node in contrast to that of Adhoc networks.

4. Network access:

In 2003, Jun et.al \cite{1241089} published about the different types of Network access used in WMNs system in their paper "The nominal capacity of wireless mesh networks". They proposed network access schemes such as backhaul access to internet and peer-to-peer (P2P) communications are supported in WMNs. In association with integration of WMNs system, a conventional wireless network can exhibit the WMNs properties and achieve performance gain for end users.

5. Power consumption Constraints:

Mesh routers are not assigned with any power constraints whereas mesh clients do require protocols with power efficient. Thus MAC or routing protocols used in mesh routers may not be suitable for mesh clients because power efficiency is primary concern for wireless sensor networks.\cite{4378303}

6. In relation with existing system:

The technologies used in WMNs system should be compatible and interoperability with the existing standard and the standard assigned with WMNs should able to support mesh-capable and conventional Wi-Fi clients. WMNs need to be interoperable with other wireless networks such as WiMax, zigbee and cellular systems.

The characteristics of WMNs system are similar to that of Adhoc networks except absence of wired connection infrastructure. Along with Adhoc networking techniques, WMNs required more developed protocols and design principles for understanding of WMNs.

Comparison of WMNs and Adhoc networks:

Wireless infrastructure/backbone: WMNs comprises of wireless backbone with mesh routers which provides connectivity, coverage and robustness in wireless domain. Nevertheless connections of Adhoc network depends on end user contributions which may be unreliable.

Integration: the technologies used in conventional clients are similar to the mesh routers. WMNs support these technologies with the help of host-routing functions managed by mesh routers and include the integration of existing networks through Gateway/ bridge functionalities.

Dedicated routing and configuration:

In adhoc networks, end-users devices exhibit the routing and configuration functionalities whereas mesh routers in WMNs perform these functions which decrease the load on end-user and also energy consumption. The end-users requirements should be limited because more number of these devices will increase the load on the system which results in more complex system and may have difficulties in data transmission. Limitation of end-users also results in cost effective of system used in WMNs.

Multiple radios:

Mesh routers in WMNs are allocated with multiple radios which are used in routing and access functionalities. The separation of two main types of traffic are enabled in WMNs systems while routing and configuration traffic is handled by mesh router and network access by end-users will be carried on other radio which results in increase in capacity whereas both these functions in adhoc networks are carried on single radio link.

Mobility:

In adhoc networks the routing protocols are managed by the end-users. Connectivity and network topology depends on mobility of end-user devices results in rescheduling of routing protocols which may vary the network configuration and the distribution. Infrastructure in WMNs system is associated with mesh routers and thus coverage of the system can be easily rearranged results in achieving high throughput along with continuous connectivity without negotiating the performance of network.

Compatibility:

WMNs system exhibit similar properties of Adhoc network along with additional features like developed routing protocols and integration of other wireless networks. In general, adhoc networks are recognised as the subset of WMNs.

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In 2004, Li et.al in their paper "On Achieving Optimal End-to-end Throughput in Data Networks: Theoretical and Empirical Studies"\cite{ 1498493 } published in Network Coding Homepage defined that all network topologies are not helpful in achieving optimal throughput even though network coding is applied which was also supported by empirical studies. They also stated the algorithms which were used in networks should be more efficient in order to achieve the optimality.

In the same year, Charikar and Agarwal \cite {1405308} submitted a paper entitled "On the Advantage of Network Coding for Improving Network Throughput" which was published in Network coding Homepage. In this paper the advantages of coding with Network coding and without Network coding were proposed and also compared the advantage of network coding with linear programming formulation of Steiner tree. This comparison was valid for both directed and undirected graph which supports that comparison is suitable for all type of networks. In case of directed networks the advantage of coding is similar to integrality gap of LP formulation in directed Steiner tree whereas for undirected networks it is equal to bidirected cut LP formulation. In 2005, Authors in \cite{1523667} proposed a data structure for studying coding and optimization of Throughput for systems having Multi layered packet transmission. The model proposed in this paper also used to examine certain physical layer phenomenon in packet erasure models that includes channel modelling and error correction coding at lower levels. The optimization of Layer by layer and cross layer rate were compared and presented in the paper. Authors in \cite{4567135} proposed different schemes which evaluate the maximum optimality of throughput for various transmission schedules at the terminals and relay nodes and different policies for throughput optimality were suggested which comprise of increasing the suitable distinction backlog for different types of coding. Based on these results, classical backpressure algorithms of plain routing were changed into analog and digital network coding. In 2007, Authors in \cite{ 4114212} introduces relaying technique for multi hop wireless networks to improve the throughput by using Network coding over bi-directional flow.

Evolution of Network coding in wireless Networks:

The concept of Network coding was first introduced in \cite{850663} and The authors in \cite{4512941} proposed COPE which was known to be first practical XOR coding system and also proposed different methods for implementation and measurement of throughput gain. In COPE ETX was considered as routing function\cite {5226634}. Based on the COPE the authors of \cite{4068276} \cite{4215706} introduces a new routing protocol for coding and also express the max flow Linear Programming (LP) for centralized approach of coding based on perfect scheduling. Chaporkar et.al proposes a complex optimization frame work for adaptive coding and scheduling in the paper entitled "Adaptive Network coding and scheduling for Maximize Throughputs in wireless networks" \cite {4509678}. Limitations of COPE were studied under practical physical layer and link-scheduling algorithms by the authors of \cite{4509678} and also proposed concept of link scheduling which is coding-efficient for practical network coding and also compared with the previous works. DCAR was the first practical Distributed Coding-aware routing system which adopts more generalized coding scheme.