Frame Relay

Voice over Frame Relay Compressing the Information on Provisioning PVCs and Benefits of Frame Relay Selected for Wireless Data on Chapter 12 Asynchronous Transfer Mode What Is Why the Interest in ATM Mapping Circuits Through an ATM The ATM Layered ATM Traffic Contention The Double Leaky Categories of Getting to the Elusive Shaping the Normal Bandwidth What Is Voice over DSL and over ATM (VoDSL and ATM Suitability for Voice Integrated Access at the Local Chapter 13 ATM and Frame Relay ATM and...

Routers Versus Gateways

A point of clarification is needed about routers and gateways. In the Internet community, routers and gateways get a little confused. In the previous discussion, we use the term router almost exclusively. As pointed out, in the Internet community, it is referred to as the default gateway. The Internet terminology started before terms were standardized. A gateway was a box that sat between two networks. Therefore, it was natural to refer to routers, especially ones connecting different networks...

Data Exchange Interface DXI

Data Exchange Interface (DXI) is another of the interfaces used to internetwork various services across an ATM backbone. Functionally, the FUNI and DXI provide the same services with minor modifications. DXI is used with legacy routers that are not ATM equipped, but use the DXI protocols and interfaces to provide frame-based services to the Data Service Unit (DSU) on the circuit where the cells are then generated. The DXI uses the DSU whereas the FUNI does not. Moreover, DXI does not use...

Jokes

Love them or hate them, but they are a reality Here again, one can offload a burdened e-mail system by creating a page exclusively for jokes to which anyone can submit a joke. Jokes are then told or sent by simply including the hyperlink to the joke on the web page. (You can palpably feel the e-mail system administrator breathing easier.) There is, of course, the problem of taste in jokes versus company policy. This can be spelled out on the jokes title or index page with a hyperlink to the...

Wdm

Ten years ago, the implementation of the OC-48 SONET specification had the industry believing that limitless bandwidth was available. One can just imagine that a mere decade ago the 2.5 Gbps capacities of the optical fiber networks was innovative and exceeded our wildest imaginations about how we would ever fill these communications channels. Yet, the industry began to recognize the changes in consumption patterns. In the demand for multimedia communications, video WAN started to erode even the...

Figure 299 The STS3 OC3 frame Add Drop Multiplexing A Sonet Benefit

Another major benefit of the SONET specification is the ability to perform add-drop multiplexing. Even though network elements are compatible at the OC-N level, they may still differ from vendor to vendor. SONET doesn't attempt to restrict vendors to all providing a single product, nor does it require that they produce one of every type out there. One vendor may offer an Add-Drop Multiplexer (ADM) with access to the DS-1 level only, whereas another may offer access to DS-1 and DS-3 rates. The...

Overview

The television broadcast signal, regardless of the standard used, is one of the most complex signals used in commercial communications. The signal consists of a combination of amplitude, frequency, phase, and pulse modulation techniques all on a 6 MHz channel with a single sideband transmission process called vestigial sideband (VSB). Cable TV appeared in the industry during the early 1960s. The initial networks installed used a basic tree architecture, in which all signals emanated from the...

The DS3 Frame Format

A two-step process is used when multiplexing to a DS-3. First, four DS-1s are multiplexed together to form a DS-2. Second, seven DS-2s are multiplexed together to form the DS-3. This is referred to as the M13 format and protocol. Literally, the same method is used to multiplex the seven DS-2s into a DS-3 as was used to multiplex four DS-1s into a DS-2. In Figure 28-12, the framing format is shown, which uses the M-13 Asynchronous Protocol. The DS-3 frame consists of seven subframes, labeled as...

ATM Traffic Management

When dealing with traffic management, some of the goals of the ATM Forum and other developers include the following ATM must be flexible. It must meet the constantly changing demands of the user population. These goals mean that the demands for traffic will rise or fall as necessary, and therefore managing this traffic is of paramount importance. ATM must meet the diverse needs of the end-user population. Many users will have varying demands for both high- and low-speed traffic across the...

The Double Leaky Bucket

In this double leaky bucket case, which was used in most of the early implementations of ATM, cells arrive from the CPE across the UNI totally uncontrollable in time. All cells leaking into the network are sent with a cell loss priority (CLP) equal to zero. As long as the arriving cells do not exceed a given rate, they are admitted to the network unchanged. If the cell arrival rate exceeds the limit imposed by the network, namely the SCR of the connection, the cells in excess of this limit have...

Mapping Circuits Through an ATM Network

ATM uses one of two connection types. The protocol is connection-oriented, so the two choices are a PVC or a SVC. There is actually no permanency to the circuits. They are logically mapped through the network and are used when needed for PVC or dial-connected when using the SVC. In either case, the carriers promise only to make a best attempt to serve the needs of the end user when the time is appropriate. With no true guarantees, the consumer is at risk (sort of). However, the concept is that...

The SS7 Network Architecture

If signaling is to be carried on a different path than the voice and data traffic it supports, then what should that path look like The simplest design would be to allocate one of the paths between each interconnected pair of switches as the signaling link. Subject to capacity constraints, all signaling traffic between the two switches could traverse this link. This type of signaling is known as associated signaling. Instead of using the talk path for signaling information, the new architecture...

BRI Application

One of the major uses of ISDN is in video conferencing. This is normally done by installing three BRI lines. The video conferencing equipment has a built-in inverse multiplexer (mux). Figure 10-9 shows a typical configuration. The three BRI interfaces are connected to the inverse mux and the control panel enables the operator to specify how much bandwidth is to be used for the videoconference. Although one could use 64 KBps for a videoconference, it is quite impractical. A minimal usable...

The Link Architecture

Signaling links are logically organized by link type (A through F), according to their use in the SS7 signaling network. These are shown in Figure 8-7 with the full linkage in place. A link An access (A) link connects a signaling end point (SCP or SSP) to a STP. Only messages originating from or destined to reach the signaling end point are transmitted on an A link. B link A bridge (B) link connects one STP to another STP. Typically, a quad of B links interconnects peer (or primary) STPs (the...

Internet Access

The hottest application for MMDS is Internet access this differs from MMDS' original application of one-way wireless cable service to deliver television programming. This application never proved popular, and most license holders are now concentrating on data service. An MMDS connection is just like any other ISP connection normally a router port with a connection for the external ISP network as shown in Figure 18-2. This is an Ethernet connection to a wireless modem. Alternatively, some...

Pulse Coded Modulation PCM

Before going any further into the DS-1, it may be appropriate to review the modulation technique used to create the digital signal. When DS-1 was first created, it was designed around converting analog voice communications into digital voice communications. To do that, voice characteristics were analyzed. What the developers learned was that voice operates in a telephony world in a band-limited channel operation. The normal voice will produce both amplitude and a frequency change ranging from...

Fiber Optics Summarized

Before proceeding too far from the beginning of DWDM, it may be appropriate to look at the fiber optic world and its relationship to the demand of the industry. Moreover, the types of fiber in use determine the capacity being delivered today, so a quick review of the variations of fiber may help to define the overall benefits of the multiplexing schemes on the glass. Fiber has been used in North America since the 1960s. The carriers recognized the limitation of the copper cable they had been...

Purpose of the SS7 Network

The primary purpose of SS7 was to access remote databases to look up and translate information from 800 and 900 number calls (now the addition of 888 and 877 area codes are included). There were several benefits to using this lookup process, such as that carriers do not have to maintain a full database at each switching node but know how to get to the remote database and find the information quickly. The second purpose of the SS7 network and protocols was to marry the various stored program...

Firewall Based VPN

The very same issues exist here as with routers. One needs to have compatible (preferably the same vendor's) firewalls at each location. Mobile users or telecommuters must have compatible VPN software. Firewalls are always potential bottlenecks, so asking them to perform VPN encryption can adversely affect all other access to your network. Here again, there is no substitute for traffic analysis. We only recommend this solution for small networks where the traffic through the firewall can easily...

Domain Name System DNS

The DNS is simply a listing of the device IP and the human-readable name (alias). A site or company usually runs two DNS systems one for the internal (protected) network and one for the external network. When a query for www.company.com arrives, the DNS returns the IP of the server (or proxy) that is designated as www. The external DNS then will only point to proxies, while the internal DNS will point to the actual servers. Internal web pages that are available or viewable by external users...

The DS3 Overhead Bits

As already stated, there are overhead bits allocated within the DS-3 frame for the purposes of aligning the frames, providing indication of stuffing and other low-level functions. These are labeled as follows F-bits The framing bits form the frame alignment for the DS-3 signal. The F-bits are located in the first bit slot in blocks 2, 4, 6, and 8 of each subframe. The frame alignment pattern is 1001 and repeated in every subframe. M-bits The multiframing bits form the multiframe alignment...

What Is Irdp In Telecomm

As the convergence of voice and data continues, a more discreet change is also coming into play. Although data is considered fixed to a location, the end user is now more mobile. This opens a new set of challenges for the industry and manufacturers alike because of the need for mobility. What once was a simple procedure of connecting the user's modem to a land line now poses the need to connect that same user to a device while mobile. Protocols need to be more flexible, accommodating the mobile...

Inside the STS1 Frame

The SPE can begin anywhere inside the STS-1 envelope. Normally, it begins in one STS-1 frame and ends there. However, it may begin in one STS-1 frame and end in another. The STS payload pointer contained inside the transport overhead points to the beginning byte of an SPE. The possibilities then are that the frame can carry a locked payload or a floating payload. Floating, in this regard, refers to the payload floating between two frames. The overhead associated with SONET is designed to let...

ATM Suitability for Voice Traffic

Sometimes mistakenly associated with Voice over IP (VoIP), VoATM is a completely separate technology that predates VoIP. In contrast to IP and Frame Relay, ATM uses small, fixed-length data packets of 53 bytes each that fill more quickly, are sent immediately, and are much less susceptible to network delays. (Delays experienced by voice in a Frame Relay or IP packet network can typically be 10 times higher than for ATM and increase on slower links.) ATM's packet characteristics make it by far...

Spread Spectrum Goals

Much of the action in the wireless arena includes the use of the frequency spectrum to its fullest while preserving its efficiency. The primary goal of spread spectrum systems is the substantial increase in bandwidth of an information-bearing signal, greater than required for basic communications. This increased bandwidth, though not used for carrying the signal, can mitigate possible problems in the airwaves, such as interference or inadvertent sharing of the same channels. The cooperative use...

Internet Operation

We have seen that the Internet is really a collection of independently owned and operated networks. The concept of networks was previously dominated by the telephone model. It had a central switching exchange and all information ran through this exchange. The telegraph network also used centralized switching. Like the telephone switching system, it, too, had telegraph lines that connected the switching centers. The telegraph-switching center was called a message switch. These message-switching...

Mobile Equipment or MS

The MS consists of the physical equipment, such as the radio transceiver, display and digital signal processors, and the SIM card. It provides the air interface to the user in GSM networks. As such, other services are also provided, which include The features' supplementary services The SIM provides personal mobility so that the user can have access to all subscribed services irrespective of both the location of the terminal and the use of a specific terminal. By inserting the SIM card into...

Purchasing Cooperatives

The capability to form purchasing cooperatives that can negotiate volume pricing with suppliers is another growing extranet application. Smaller businesses from parts stores to building contractors can pool their requirements and approach the supplier with volume deals. The second major advantage is getting the orders correct. This almost can't be emphasized enough. It can take a full-time employee to verify orders, process the paperwork, send back the incorrect stuff, and get credit for it...

Overall Frame Relay Core Protocols

When the Frame Relay specification was developed, the primary goal was to carry data over the WAN. To handle this form of wide area communications, the core protocols for Frame Relay were established using the revised version of the data link protocols. Instead of using the network layer protocols, Layer 3 was gleaned down to efficiently carry the traffic while performing the same function as the network layer. Moreover, the data link layer was also streamlined to offer less overhead and...

Virtual Tributaries

SONET is more than the STS frame it also defines the sub-STS levels of payload that can be carried. The STS-1 payload can be subdivided into virtual tributaries, synchronous signals to transport lower-speed signals. The normal sizes defined by SONET are shown in Table 29-6. Table 29-6 The values of the virtual tributaries defined for SONET Table 29-6 The values of the virtual tributaries defined for SONET

Satellite Installations

In Table 26-1, a list of the satellite installations by country is shown. The list shows the main providers and users of satellite transmission systems. Table 26-1 Number of satellites in orbit by country around the world Table 26-1 Number of satellites in orbit by country around the world The technological and regulatory hurdles to create true high-speed satellite networks are fast becoming past tense. Low- and mid-bandwidth systems such as Motorola's Iridium and Hughes' DirecPC can handle...

The Mobile Telephone Switching Office MTSO

The MTSO is a Class 5 Central Office (CO) equivalent. It provides the trunks and signaling interfaces to the wireline carriers. It has a full-line switching component and the necessary logic to manage thousands of calls simultaneously. Like the CO infrastructure, the MTSO uses digital trunks between the MTSO and the wireline carriers (Incumbent Local Exchange Carrier ILEC , Competitive LEC CLEC , or Interexchange Carrier IEC ) either on copper, fiber, or microwave radio systems. At the MTSO,...

GSM Network Connection to SS7 Networks

The MSC is the Central Switching function of the GSM network. The MSC is connected to a SS7 network for the purpose of signaling and performing database queries. The SS7 network uses a network node called the STP, which is a packet switching node (can be SS7, IP, or X.25). Using a 64 Kbps channel connection between STPs, the network can process its signaling information. Next in a SS7 network is the use of the SCP, which houses the databases congruent to the network. In many cases these...

Logical Channels

GSM distinguishes between physical channels (the time slot) and logical channels (the information carried by the physical channels). Several recurring time slots on a carrier constitute a physical channel, which is used by different logical channels to transfer information both user data and signaling. A channel corresponds to the recurrence of one burst every frame. It is defined by its frequency and the position of its corresponding burst within a TDMA frame. GSM has two types of channels The...

Low Earth Orbit

In December 1990, Motorola filed an application with the FCC for the purposes of constructing, launching, and operating a LEO global mobile satellite system known as Iridium. This was the hot button that sparked the world into a frenzy. Iridium was a concept of launching a series of 66 satellites 1 Originally the Iridium proposal was for 77 satellites, but Motorola amended this number after the World Administrative Radio Council meeting in the spring of 1992. around the world to provide global...

Overlapping Coverage

Each cell has its own radio equipment with an overlap into adjoining cells. This allows for the monitoring of the adjacent cells to ensure complete coverage. The cells can sense the signal strength of the mobile and hand-held units in their own areas and in the overlap areas of each adjoining cell. This is what makes the handoff and coverage areas work together. The graphic in Figure 20-6 shows the overlap coverage in the 7-cell pattern described previously. Figure 20-6 Overlap coverage between...

The OSI Protocol Stack and Frame Relay

When we discuss the use of the data link protocols, one always compares the Open Systems Interconnection (OSI) to whatever other protocol is being discussed. This book is no different because one needs to understand where Frame Relay falls on the OSI stack and what Frame Relay's purpose is. The development of any new set of standards is usually done to improve network performance. Frame Relay works at the data link layer to reduce the overhead associated with the movement of data across the...

GSM Architecture

A GSM network consists of several functional entities whose functions and interfaces are defined. Figure 21-9 shows the layout of a generic GSM network. The GSM network can be divided into three broad parts. The subscriber carries the MS, the Base Station Subsystem (BSS) controls the radio link with the MS, and the Network Subsystem, the main part of which is the Mobile Switching Center (MSC), performs the switching of calls between the mobile and other fixed or mobile network users, as well as...

Signal Level

The cable system requires certain parameters in order to function properly. Originally distributed via a microwave distribution (still done in some cases) and coaxial cables, the systems are under constant scrutiny and change. Throughout the CATV system, power is distributed in the form of Specified levels must be maintained at each point in the system to assure good performance. The signal levels at different frequencies are just as important. Here is how they are measured Cable TV uses FDM...

The Multiplexing Scheme

When trying to understand the SDH architecture, it is important to remember that the North Americans have always done things one way and the Europeans (actually, the rest of the world) have done things in a different way. The two entities never seem to become harmonized. As a result, the way the mapping and multiplexing was arranged differs from the way the standards and multiplexing techniques work in the North American communities (ANSI and SONET). The language differs from what is used in...

Benchmarks in GSM

Table 21-1 shows many of the important events in the rollout of the GSM system other events were introduced, but had less significant impact on the overall systems. CEPT establishes a GSM group in order to develop the standards for a pan-European cellular mobile system. A list of recommendations to be generated by the group is accepted. Field tests are performed to test the different radio techniques proposed for the air interface. Time Division Multiple Access (TDMA) is chosen as the access...

Shaping the Traffic

The ITU-TSS defines four possible situations when a cell enters an ATM network Successfully delivered The cell arrives at the destination with less than time T-cell delay. An errored cell occurs A cell arrives with at least one detected bit error in the information field in the cell. Another possibility is the severely errored cell with information bits errors equal to n or n> 1. Lost cells A cell either never arrives or arrives after the time T-cell delay, in which case it is discarded at...

Routing Versus Switching

There is a good deal of confusion over the issue of routing versus switching. Now that we have discussed and given examples of each, let's see if we can make a clear distinction. This section began with a discussion of X.25 and packet switch. In X.25 we used the first packet to contain the address. That packet had to be routed to find the destination. In the process of doing the routing, a virtual circuit was set up by using the LCN that was now carried in every packet in lieu of the address....

Enter LMDS

LMDS, as its name implies, is a broadband wireless technology that is used to deliver the multiple service offerings in a localized area. The services possible with LMDS include the following Just as the network providers were getting used to the battlegrounds between the ILECs and the new providers, RF spectrum was freed up around the world to support access and bypass services. Typically, the services operate in the RF spectrum above 25 GHz, depending on the licenses and spectrum controlled...

Pros and Cons to Wireless

Some of the inherent problems bring other solutions and benefits to the table. For example, when using a wireless interface, the user is mobile and can go almost anywhere at whim. This allows more flexibility. However, the downside is that the use of cellular and Personal Communications Services (PCS) systems causes data and call handover to occur, which can be detrimental to the overall performance. Security issues cannot be ignored with data in the air. On a copper cable, data is slightly...

Automating Customer Service

The two issues to be addressed here are the following Improving the responsiveness of our customer service organization or function Reducing the cost of providing the service (Some companies have found the ideal solution. They charge their customers to provide service that a well-designed product wouldn't require.) The basic problem is that having technical folks respond to e-mail customer service queries is boring for the individual. They soon develop a bad attitude and quit. Having...

The ATM Layered Architecture

Moving Atm

Nearly all documents describe the layered architecture of every protocol against the OSI model as a reference only. The ATM architecture is no different when trying to compare what the protocol is doing. Using the OSI model as a base reference, the ATM layers fall typically in the bottom two layers (data link layer and physical layer) of the architecture. ATM has been designed to run on a physical medium such as SONET. In Figure 12-8, the ATM layer is shown as the bottom half of Layer 2 in its...

Universal Resource Locator URL

The URL is simply the Internet address of the web page. URLs are displayed in this form http www.tcic.com . This URL takes you to TCIC's main web page. Selecting a hyperlink from that page takes you to a Universal Resource Identifier (URI), which points to the files in the directory tree of the host server. Each slash ( ) in the name identifies a directory level on the server. In some cases where a document management system is employed to build and provide web pages, these slashes are actually...

Inventory Management Wholesale

The first example of an extranet is a wholesaler who must maintain inventory to handle transient demand as well as his contract quantities. The normal cost of distribution is about 18 percent of the cost of goods. This can be reduced to about 5 percent with the application of an extranet and electronic commerce. The wholesalers can now do just-in-time inventory control. Depending on the goods involved, the wholesaler may be able to get overnight shipment from providers, thus reducing the need...

XDSL Coding Techniques

Many approaches were developed as a means of encoding the data onto the xDSL circuits. The most common are Carrierless Amplitude Phase Modulation (CAP) and discreet multitone (DMT) modulation. Quadrature with Phase Modulation (QAM) has also been used, but the important part is the standardization. The industry, as a rule, selected DMT, but several developers and providers have used CAP. It is, therefore, appropriate to summarize both of these techniques. The SHDSL technology uses a...

Creating the VPN

There are five ways to create a VPN Although not normally considered a VPN, one can certainly use desktop PCs to encrypt data and send it across the Internet securely. Additionally, software is available that runs on a desktop capable of creating a VPN to a firewall or stand-alone VPN device. Most VPN equipment vendors offer corresponding software that runs on a laptop or desktop in order to provide a secure path to the home office over the Internet. Most of the discussion then involves...

The Difference Between Tx and DSx

In many cases, the terms become problematic because we tend to intersperse them. Therefore, when discussing the different services, it becomes imperative to discuss the difference between a T-x and a DS-x. T-x (such as T-1 and T-3) refers to the services acquired from a carrier or local provider by physical layers one and two. The T carrier is a physical set of wires, repeaters, connectors, plugs and jacks, and so on. When referring to a T-1, we are actually describing the physical layer...

Hyperlink

A hyperlink is simply a pointer to another web page. It is the complete address to find the specified web page. The link visible on the browser-presented web page might say something innocuous like more info. If you view the source and search for the HREF or the more info, following the HREF5 will be the actual path to that page. Selecting the hyperlink caused a lot of background processing. The browser took the Universal Resource Locator (URL) and fabricates a query to that location just as...

Subnet Masking

To be assured that we can separate the address space, each system in the subnet must have the same subnet mask. The subnet mask distinguishes between the network bits, subnet bits, and interface (host) bits. To do this, the mask must have the same number of bits as the IP address and is in the same format as the IP address. Though the mask has the same format as the IP address, its first byte always has a value of decimal 255, which is impossible for any IP addressable interface. A network...

Advantages

Although satellites have certain disadvantages, they also have certain advantages over terrestrial communications systems. Satellites have a natural broadcast capability. Satellites are wireless, so they can reach geographically remote areas. There are major changes occurring in the design of communications satellite systems. New bandwidth-on-demand services are being proposed for GEO. The Federal Communications Commission constantly receives filings for new Ka-band satellite systems each year.

Sectorized Cell Coverage

Directional (sectorized) sites use reflectors positioned behind the antenna to focus the coverage area into a portion of a cell. Coverage areas can be customized to the needs of each site, as shown in Figure 20-8, but the typical areas of coverage are as follows Two sectors using 180-degree angles Three sectors using 120-degree angles Six sectors using 60-degree angles At least one transmit antenna is used in each sector (one per radio frame) and two receive antennae provide space diversity for...

GSM Metrics

The GSM standard is the most widely accepted standard and is implemented globally, owning a market share of 69 percent of the world's digital cellular subscribers. Time Division Multiple Access (TDMA), with a market share close to 10 percent, is available mainly in North America and South America. GSM, which uses a TDMA access, and North American TDMA are two of the world's leading digital network standards. Unfortunately, it is currently technically impossible for users of either standard to...

Applications That Demand Mobile IP

What are the applications that will take advantage of the mobility of the user Well, the first one is going to follow our example for mail. But e-mail is only one of many applications that users will want to use. Other areas will include transaction processing (orders online), fax capabilities, File Transfer Protocol (FTP), and Telnet. Telemetry applications and multimedia are all prime candidates. This is shown in Figure 23-6 where the applications will be paramount to the ability to move...

T2 Transmission or DS2

For all its work, the T-1 was a beginning step to the North American Digital Hierarchy. From there, other multiplexing steps were instituted to get higher speed communication services. A second means of achieving the high-speed communication is to multiplex four DS-1s into a DS-2. The DS-2 (physically, it is a T-2) is a data channel carrying 96 channels of 64 Kbps each, plus overhead yielding a nominal 6.312 Mbps data transmission speed. To create the DS-2, four DS-1 signals are combined. This...

Extranet

We are connected to the Internet and specifically permit access to our network (or portions of our network) by our customers. We are now at risk from all sorts of hackers, crackers, and freaks. The goal then is to keep them out (or at least slow them down and make them work for it) while giving our friends and customers free, that is, unfettered, access. The first step then is to install a firewall. A firewall is simply a machine whose job it is to examine each packet arriving and verify...

List of Figures

Figure 3-1 Hub and spoke arrangement for TIE lines Figure 3-2 The VPN uses the PSTN as the backbone Chapter 4 Data Virtual Private Networks (VPNs) Figure 4-1 Tunnels provide secure access for VPNs. Figure 4-2 Competitors may actively pursue your data. Figure 4-3 Hackers break in just to prove their prowess. Figure 4-4 The pieces that must be considered for security Figure 4-5 Security key management is used for IPSec. Figure 4-6 The L2TP packet Figure 4-7 The various forms of IP packets Figure...

The Base Transceiver Station BTS

The BTS (see Figure 21-12) houses the radio transceivers that define a cell and handles the radio link protocols with the MS. In a large urban area, a large number of BTSs may be deployed. The requirements for a BTS are The BTS corresponds to the transceivers and antennas used in each cell of the network. A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell. Each BTS has between 1 and 16 transceivers, depending on the density of users in the cell....

Number Administration and Call Routing in the Network

Telephone numbers in a pre-LNP environment have always been assigned to Local Service Providers' end offices on an area code and exchange code (Numbering Plan Area NPA-NXX ) basis. Each NPA-NXX contains 10,000 telephone numbers. Because an NPA-NXX is only served by a single end office in the United States, the telephone number identifies the person as well as the actual end office that serves that person. In effect, the dialed NPA-NXX is the terminating switch's routing address to the rest of...

Advantages of Using MMDS

The following list includes some advantages of using MMDS It has chunks of under-utilized spectrum that will become increasingly valuable and flexible. System implementation, which is little more than putting an installed transmitter on a high tower and a small receiving antenna on the customer's balcony or roof, is quick and inexpensive. Because MMDS services have been around for 30 years, there is a wealth of experience regarding the use and distribution of the services. A single tower can...

History of Cellular Mobile Radio and GSM

The idea of cell-based mobile radio systems appeared at Bell Laboratories in the early 1970s. However, the commercial introduction of cellular systems did not occur until the 1980s. Because of the pent-up demand and newness, analog cellular telephone systems grew rapidly in Europe and North America. Today, cellular systems still represent one of the fastest growing telecommunications services. Recent studies indicate that three of four new phones are mobile phones. Unfortunately, when cellular...

What Is Outof Band Signaling

Out-of-band signaling is signaling that does not take place in the same path as the conversation. We are used to thinking of signaling as being in-band. We hear dial tone, dial digits, and hear ringing over the same channel on the same pair of wires. When the call connects, we talk over the same path that was used for the signaling. Traditional telephony used to work this way as well. The signals that set up a call between one switch and another always took place over the same trunk that would...

The Analog Modem History

In the early days of modem communications, the Bell telephone companies (or the independent telephone companies) provided all services across North America. A customer desiring to transmit data needed only to call the local supplier who would then install the dial-up telephone line, the modem, and all associated services to accommodate the desired data rates available. Leased lines were used when specific speeds or volumes were anticipated, but not guaranteed by the dial-up services. Regardless...

Allocation of Frequencies

The allocation of frequencies based on the first cellular arrangement of AMPS was designed around 666 duplex channels. The frequency ranges were allocated in the 825 845 MHz and 870 890 MHz frequency bands. In each band, the channels use a 30 kHz separation, and 21 channels are allocated to control channels. Figure 20-10 is a representation of the channel allocation. Figure 20-10 Frequency allocation for cellular The FCC approved licenses for two operators of the cellular service the wireline...

Establishing a Call from a Landline to a Mobile

Network Establishment For Mobile

From a wired telephone, the local exchange office pulses out the cellular number called to the MTSO over a special trunk connecting the telephone company to the MTSO. The MTSO then analyzes the number called and sends a data link message to all paging cell sites to locate the unit called. When the cellular unit recognizes the page, it sends a message to the nearest cell site. This cell site then sends a data link message back to the MTSO to alert the MTSO that the unit has been found. This...

Voice over DSL and over ATM VoDSL and VoATM

In general, a VoDSL system functions as an overlay solution to a DSL broadband access network, enabling a LEC or CLEC to extend multiline local telephone service off of a centralized voice switch. For example, some VoDSL solutions enable up to 16 telephone lines and high-speed continuous data service to be provided over a single digital subscriber line (DSL) connection. A VoDSL solution typically consists of three components First, a carrier-class voice gateway that resides in the regional...

Wide Area Information Service WAIS

Wide Area Information Service (WAIS) was another database search engine that allowed you to enter keywords and search a database for entries. Although the number of databases was large, finding this was still not easy because you were using Gopher to search WAIS. The World Wide Web (WWW) has essentially replaced all of these older search engine capabilities. The early WWW often resorted to Gopher or WAIS to actually do the transfer. The two developments that made the WWW useful were browsers,...

Frame Relay Selected for Wireless Data on GPRS

Newer wireless services known as the General Packet Radio Services (GPRSs) are designed around the movement of IP datagrams (always-on Internet access) from a cell phone or personal digital assistant (PDA) to the public Internet or a VPN connection to an intranet. Regardless of the direction that the data is going to flow, the use of the IP services from the handset enables us to use the network ad hoc. When an IP is created, it is packaged in a radio message. Once this message gets to the base...

Benefits of SVCs

Some public Frame Relay services' pricing structures are forcing end users to build star networks even when the underlying traffic patterns warrant more meshing. Some pricing structures incant high subscription rates on ports, which result in star and hub-and-spoke configurations. For example, all remote offices may have direct connectivity to the headquarters location only. Remote-office-to-remote-office communication happens by tandeming through the headquarters router. The headquarters...

Frame Relay Defined

First, a definition of packet switching is in order because Frame Relay falls into the category of a packet-switching family. Packet switching is a store and forward switching technology for queuing networks where user messages are broken down into smaller pieces called packets. Each packet has its own associated overhead containing the destination address and control information. Packets are sent from source to destination over shared facilities and use a statistical time-division multiplexing...

Framing Bits for the DS2

Framing bits F-bits form the frame alignment much the same as the DS-1 framing bit. There are a total of eight framing bits in a DS-2 frame two in each subframe . F-bits are located in the first bit position in blocks 3 and 6 of each subframe. The frame alignment pattern is 01, which repeats every subframe. The F-bits are shown in Figure 28-11. Other overhead bits are also shown in the framing pattern. These include the following Figure 28-11 The DS-2 overhead bits shown Figure 28-11 The DS-2...

Location Area

A location area LA , identified by its location area identity LAI number, is a group of cells served by a single MSC VLR. One MSC VLR combination has several LAs. The LA is part of the MSC VLR service area in which a MS may move freely without any updating of location messaging to the MSC VLR controlling the LA. A group of LAs under the control of the same MSC VLR defines the MSC VLR area. A single PLMN can have several MSC VLR service areas. MSC VLR is a sole controller of calls within its...

Modulation and Access Techniques

As already discussed, the modulation and access method falls into two primary categories, FDMA and TDMA. Each of these techniques differs but also creates other submodulation capabilities. For the broadband LMDS services, the system is usually separated into both phase and amplitude modulation of the RF. Phase-shift keying PSK and amplitude modulation combinations have been successfully used to achieve high rates of multiplexing and carrying capacities. The options of using FDMA and TDMA are...

Introduction to SS7

The ITU-TS once called the CCITT developed a digital signaling standard in the mid-1960s called Signaling System 6 SS6 that would revolutionize the industry. Based on a proprietary, high-speed data communications network, SS6 later evolved to SS7. SS7 has now become the signaling standard for the world. The success of the signaling standards lies in the message structure of the protocol and the network topologies. The protocol uses messages much like the X.25 and other message-based protocols...

Info

Figure 19-3 SMR base station and radio service When a mobile set is powered on, it automatically registers using the CC. Once the subscriber receives a positive acknowledgement from the network, the mobile is registered on the trunked radio system and can be used. The mobile is constantly in contact with the CC. If there is a call request, the trunked radio system checks whether the addressed subscriber is available. If he is not available, not registered, or engaged, this information is given...

Access Methods

Because radio spectrum is a limited resource shared by all users, a method must be devised to divide up the bandwidth among as many users as possible. The choices are Code Division Multiple Access CDMA GSM chose a combination of TDMA FDMA as its method. The FDMA part involves the division by frequency of the total 25 MHz bandwidth into 124 carrier frequencies of 200 kHz bandwidth. One or more carrier frequencies are then assigned to each BS. Each of these carrier frequencies is then divided in...