The Cable Cordect System

Published Date: 02 Nov 2017

Abstract— As the requirement of internet is increasing day by day along with the need of high speed data download, this report about a technology "Cable-corDECT" which provides very high data download speed and that too at a very cost effective price. In this report we will be discussing about this technology, the working mechanism, equipments used, along with this I have also included my understanding about this technology and suggested certain measures which if incorporated will certainly improvise it. During the course of my work I was able to visit many customers who are using internet on corDECT phones and could see what exactly they feel about this in terms of service and data quality. The best effort has been put in writing this report to make it simple and understandable.

Introduction

Cable-corDECT is one of the most cost-effective technologies designed to serve phone and internet requirement of the customer. This technology is designed keeping in mind the practicality of requirement of internet i.e. generally if we see; we will find there is more of downstream data as compared to the upstream data when internet is used. So it is designed to support very high data download speed and comparatively low upload speed. The downstream of data in this is through RF cable which normally nowadays is found in almost all the houses, because of increasing use of cable TV. This RF cable has the capacity to support very high data transfer, but when only TV signals are used this cable is not used completely, so this same cable is used for the downstream of internet packets. The IP packets are converted to MPEG form with the help of a modulator PC and are mixed with the TV packets at the Local Cable Operator (LCO) or Head End. Now at the customer premises these IP packets and MPEG packets are separated from each other with the help of a BRM (Broadband Receiver Module) Box and can be fed to TV, PC and Phone.

The upstream of data if done through the same RF cable adds a little complexity to the system since then IP packets must be converted to a particular frequency to be transferred through RF cable, which will add the setup cost at Customer Premises. Therefore this upstream of data, is done wireless through the same setup as that of corDECT phones. While handling data call (Internet) the corDECT phone has the capability to support voice call also and that too without hindering each other. This setup works on PPPoE (Point to Point over Ethernet) Protocol. The initial authentication packets both the upstream and downstream are through the wireless medium, once the call is authenticated and connection is established the downstream is done through RF cable and upstream wireless whereas for a voice call all the packets go through wireless medium. The WLL phone too has lot of advantage over normal wired phones.

Traditionally, a pair of copper wires is used to connect each telephone subscriber to the nearest exchange. Such a wired local loop poses the following problems:

The laying and maintenance of copper cable up to the subscriber’s premises incurs high cost. The wired local loop contributes about one-third of the cost in providing a line to a subscriber. Also, this cost is increasing with time as the cost of copper increases.

The per-line cost for rural areas is significantly higher due to the large amount of cabling infrastructure required to take even a few telephone lines to remote villages.

Most faults are in the local loop, due to water-logging, damage or theft of cables.

Rapid deployment is difficult owing to the regulatory and other problems in laying buried cables.

Wireless technology can provide a cost-effective solution to the local loop problems. The wireless service facilitates easy expansion of the network as installation is easier. Further, the cost of wireless technologies is primarily in electronics and is expected to come down with time. In order to be useful in urban areas of developing countries such as India, the wireless local loop technology must cater to high subscriber densities of 1,000–10,000 subscribers/sq.km. It must also provide toll-quality voice and data and FAX capability on par with a wired telephone.

Need of New Technology

Till around the mid-eighties, a local loop or an Access Network (AN) used to consist of a pair of copper wires connecting the subscriber at home or office to the nearest exchange. The local loop length in urban areas would be typically as long as 6 to 8 km and the diameter of the copper used was 0.5 mm to 0.6 mm. The loop was designed to carry 0 - 4 kHz voice and was difficult to maintain, with almost 85% of all faults found in the local loop. Above all it was expensive, as well as difficult and time-consuming, to deploy. With copper and digging costs increasing every year, if one were to continue with such an approach, the per-line local loop cost itself would today amount to over 80% of the total cost of putting up a telecom network.

Access Network

Fortunately, an uncelebrated but major technological innovation changed the Access Network from mid-eighties onwards. As shown in Figure 1.1, the AN now consists of an

optical fibre from an exchange to a Remote Line Unit (RLU) and typically a 3 - 4 km copper loop from the RLU to the subscriber premises.

The internet tangle

The Internet has emerged as second only to the telephone in connecting people and may tomorrow subsume the telephone network. But today, Internet access at homes and offices largely rides on the telephone network.

Figure Internet access using the telephone network

Wireless Local Loop Vs. Mobile Wireless Access System

Today, there is little doubt that wireless access systems should provide digital and not analog access. Wireless connectivity to subscribers today is provided by mobile communication systems as well as wireless local loop systems. These two appear to be similar and are often confused with each other. However, the requirements for the two systems are significantly different.

corDECT WLL Architecture and Implementation

The DECT standard used by the corDECT system is designed for high density, micro-cellular systems that support voice telephony, high speed data, video and other multimedia applications. The main features of the DECT standard are:

DCS, a process whereby the portable continuously scans all the channels and dynamically selects better channels when they become available.

Roaming anywhere in the radio coverage network.

Seamless bearer (or channel) handover from channel to channel or from cell to cell. This is transparent to the user even during a conversation.

Authentication and encryption, which provide a high-level of security and privacy.

The DECT Protocol Stack

The DECT standard has been structured according to the Open Systems Interconnection (OSI) model. DECT has defined four protocol layers for the air-interface. These correspond to the lower three layers of the OSI model. The functionality of these layers is discussed below:

Physical (PHL) Layer

This layer specifies the radio frequencies and transmission characteristics, the division into 10 ms frames and subdivision of each frame into 24 slots. It monitors the quality of signal in all slot and frequencies used by the DECT equipment.

Medium Access Control (MAC) Layer

This layer provides connections used for user data and some control, connectionless channels for control information flow and broadcast service to page a portable. It handles handover of a connection from one channel to the other due to link quality degradation (within a CBS), called bearer handover.

Data Link Control (DLC) Layer

Using bearers provided by the MAC layer, the DLC layer creates and maintains reliable

connections, provides connection-oriented and connection-less service to higher layer, handles handover of a connection at portable from one CBS to the other due to link quality degradation or CBS failure, called connection handover.

Network (NWK) Layer

This layer establishes, maintains and releases calls (Call Control), handles mobility management, registration and authentication of portables. This layer along with MAC and DLC supports encryption of signaling, user voice/data information.

Performance Evaluation

In this work, we study the performance of DIU and CBS of the corDECT system. An analytical model of the corDECT system that could fairly accurately predict the performance characteristics of the system is developed. The model is used to study the system capacity, to identify and improve the bottleneck subsystem, to examine the feasibility of expanding the capacity of the system and to investigate the feasibility of supporting data in addition to voice in the corDECT system.

Performance measurements with a large system such as a 1,000-line corDECT system are difficult. Hence, we develop a simple Queuing Network Model that can be efficiently used to study the corDECT Architecture. Mean Value Analysis (MVA) is an efficient solution technique for networks of queuing centres. The exact MVA technique is used to solve the corDECT Analytical model.

Fig. Sequence of events in a job

corDECT problems at Customer Premises

The chapter contains the information about customers who faced internet related problems in the corDECT network of Shyam Telelink, so that common problems can be understood so as to minimize, and in future, eliminate these kinds of problem, so the utilization of manpower can be done in some other constructive work and best services can be delivered to the customers.

These are the few points which may be adopted so as to provide better services to our customers:

CD containing the setups of PPPoE dialer can be given to the customers when they start this service as it is given by ISP’s which give normal dial-up service, so that in future we do not have to go back to them in case they loose there dialer.

Node people should be given proper training with the proper procedure so as to install or in case of problem detect the exact point of problem. For e.g. before installing PPPoE they must first check the connectivity from Computers LAN card to ALM and incase of problem try to rectify it instead of trying to install dialer again and again.

Some kind of packet filtering mechanism may be introduced at customer premises so as to block broadcast packet from virus affected PC’s.

Our corDECT system should be able to support majority of Ethernet adapters available in the market.

The Microsoft drivers for LAN card must be supported, in some cases it is found that these drivers are not supported.

Mechanism for knowing weather IP service is active on a particular number or not from customer premises.