Term
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Definition
| Many sine waves with a combination of frequencies from the lowest to the highest that a circuit can carry. |
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Term
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Definition
| Public Switched Telephone Network - The modern digital telephone network system supports long distance dial-up service for data communications. |
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Term
| POTS (Plan Old Telephone System) |
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Definition
| The old telephone network system employed analog transmission methodologies to transmit the voice signals from source to destination. |
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Term
| Basic Telephone System Infrastructure |
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Definition
Components of PSTN
* Local Loop (any connection from user to CO)
*LEC (Local Exchange Carrier)
*CO (Central Office) - (belongs to LEC)
*Telephone Switch (located in the CO)
*ICE or IXC (Inter Exchange Carrier)
*POP - Point of Presence - belongs to the IEC
*Tandem Switch - located in the POP
*LATA - Local Access Transport Area
Any call between two areas must go through a POP |
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Term
| Basic Telephone Infrastructure |
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Definition
| Phone - Local Loop - CO - Trunk Line - POP - Inter-exchange circuit - POP - Trunk Line - CO - Local Loop - Phone |
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Term
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Definition
Like a small central office. The lowest level in the telephone switch hierarchy.
Digitizes voice and data.
Connect off hook lines through to the local exchange - the concentration function
Multiplex, interleaving many calls together on a single wire or optical fiber.
* Concentrators are often co-located with a Digital Subscriber Line Access Multiplexer (DSLAM) - For ADSL internet service
*Trunk line is switching calls from one CO to another. |
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Term
| Telephone Call Characteristics |
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Definition
Calls can be:
Intra-LATA
Inter-LATA
LATA = (Local Access Transport Area)
Local Loop is analog in character
Trunk line is digital in character
Inter-exchange circuit is digital in character. |
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Term
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Definition
Purpose - To ensure smooth operation, network elements need to:
*Identify themselves
*Communicate their status (on/off hook, busy signal)
*Pass instruction
* Billing
* Network mgt info (e.g., remote monitoring, diagnostics, etc.) |
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Term
| Four Basic Functions of Signaling |
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Definition
1. Alerting
2. Addressing
3. Supervising
4. Controling |
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Term
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Definition
| The signal is sent from the phone through the local loop to the CO. |
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Term
| Addressing (in a Touchtone phone) |
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Definition
Dual Tone Multi-Frequency (DTMF)
A combination of frequencies makes the sounds that correspond with each number. |
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Term
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Definition
3 basic parts of US calls
3-digit area code
3-digit exchange
4-digit subscriber number |
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Term
| International Number Plans |
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Definition
011 - The 0 exits the LATA
Country Code
City Code
City Number |
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Term
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Definition
Each are code can support 1000 exchanges
Each exchange can support 10,000 numbers
So each area code can support 10 million numbers (1000 exchanges x 10,000 numbers in each exchange) |
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Term
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Definition
Exhausted by fax machines, cell phones, VoIP numbers.
N11 and N00 reserved for special services (e.g., 911, 800, 900)
New Issues - Number portability allows users to take their numbers with them when changing to another local carrier |
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Term
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Definition
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Term
| Voice Digitization in the POTS |
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Definition
*POTS was traditionally analog
*Current POTS combines both analog and digital
*Digital v. Analog -
*Analog signal - continously varying electromagnetic wave
*Digital Signal - a sequence of discrete electrical voltage |
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Term
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Definition
| Electrical Pulse can be varied to represent characteristics of an analog voice signal. |
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Term
| 5 Different Voice Digitization Techniques |
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Definition
PAM - pulse amplitude modulation
PDM - pulse duration modulation
PPM - pulse position modulation
PCM - pulse code modulation (the most common digitization technique)
ADPCM - Adaptive differential PCM: CCITT standard |
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Term
| PAM: Pulse Amplitude Modulation |
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Definition
Variable: Pulse amplitude
Constants: Pulse duration and position |
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Term
| PDM: Pulse Duration Modulation |
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Definition
Variable: Pulse duration
Constants: Pulse amplitude and position |
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Term
| PPM: Pulse Position Modulation |
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Definition
Variable: Pulse position
Constants: Pulse duration and amplitude |
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Term
| Decentralization of the Switch |
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Definition
PBX (Private Branch Exchange)
KTS (Key Telephone System)
Centrex (Central Exchange) |
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Term
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Definition
Private Branch Exchange - Intended for large organizations
Basically an organization bought a CO. This is decentralization. So you have a switching device to get calls to eachother without going out to the trunk line. |
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Term
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Definition
Key Telephone System
Doesn't go through a central office. Phone has features within it. |
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Term
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Definition
Central Exchange - Intended for very large organizations
PBX like features with much more capacity and processing power.
Offer access to CLASS (Customer Local Access Signaling Services) |
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Term
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Definition
Simplex -> (Going one direction)
Half Duplex -> Going both directions, <-
but one at a time
Full Duplex <-> two ways at the same time. |
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Term
| Digital Cellular Technologies |
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Definition
| 1G through 3G using varying technologies for switching |
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Term
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Definition
| AMPS - Analog Circuit Switched |
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Term
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Definition
Digital circuit switched
GSM
TDMA
CDMA |
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Term
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Definition
Digital Packet Switched
GPRS,
CDMA2000 and 1XRTT
EDGE |
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Term
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Definition
Digital Packet Switched
CDMA2000, 1XEVDO, and 1XEVDV
WCDMA |
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Term
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Definition
Advanced Mobile Phone Service
832 frequencies to use in a city across 395 channels. EAch cell can have 57 conversations. Uses FDMA |
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Term
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Definition
Frequency Division Multiple Access - Used by Advanced Mobile Phone Service (AMPS).
Half the freq. range for receiving
Half the freq. range for transmitting.
Bands divided into 30 KHz sub-bands called channels |
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Term
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Definition
Uses multiple low power transmitters (100w or less)
Area is divided into cells |
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Term
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Definition
| A unit of coverage area served by a transmitter/receiver. The basic building block for of the cellular system. |
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Term
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Definition
| Mobile Unit / Mobile Equipment (e.g., a cell phone) |
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Term
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Definition
| Base STation - includes a controller and a number of receivers |
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Term
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Definition
Mobile Telecommunications Switching Office (MTSO)
The equivalent of a central office for a PSTN. It is a physical box on top of the tower. |
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Term
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Definition
| Go from ME -> BS -> MTSO -> PSTN |
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Term
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Definition
ESN is the Electronic Serial Number - a unique 32 bit # programmed into the phone when it is manufactured.
MIN is the Mobile Identification Number - It is a 10-digit number derived from your phone's number.
SID - System Identification Number - a unique 5-digit number that is assigned to each carrier by the FCC
While the ESN is considered a permanent part of the phone, both the MIN and SID codes are programmed into the phone when you purchase a service plan and have the phone activated. |
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Term
| How does a cell phone call work? |
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Definition
* Power UP - Phone talks to BS through Control Channel
* Network Identified though SID
* Phone registers itself - network keeps track of location
* If someone calls you, system checks database to see where you are.
*MTSO picks up a pair of frequencies for call
*Sends instruction to phone over control channel (one of the BS channel types) |
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Term
| Example of Mobile Cellular Call |
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Definition
ME monitors for strongest signal
Request for Connection is made (from MTSO)
MTSO pages nearby towers
MTSO connects call through the applicable tower.
If the location changes to a nearby cell, there is a handoff. |
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Term
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Definition
Cell Size
Frequency Re-Use
Hand-off
Roaming |
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Term
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Definition
Typically 10 square miles
Normally thought of as hexagons
57 conversations within a cell (AMPS) |
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Term
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Definition
| Same channel frequency can be used in non-adjacent cells |
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Term
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Definition
| When user moves to other adjacent cell and is automatically associated with BS of that cell |
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Term
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Definition
When user moves beyond coverage area of entire cell network into remote area.
Network in remote area contacts home network to verify that user can make calls and is charged appropriately. |
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Term
| Multiple Access Approaches |
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Definition
FDMA - Frequency Division Multiple Access
TDMA - Time Division Multiple Access
CDMA - Code Division Multiple Access (2G) |
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Term
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Definition
| EAch call on its own frequecy |
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Term
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Definition
| Each call on its own time slot. |
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Term
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Definition
| All calls on same frequency but each modulated by unique code, which towers reassemble |
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Term
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Definition
IP packet switched networks
100 Mbits per second for low mobility
1G/s for low mobility
Mobile WiMax
LTE - Long term evolution - A new standard for wireless |
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Term
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Definition
Voice over Internet Protocol
LAN or WAN
It is packet switched
Saves costs
Improves facilities |
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Term
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Definition
1. Companies can save money -voice over internet instead of telcomms
2. Companies can devise improved methods or working with customer service |
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Term
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Definition
Pros
*Less waste
*lower costs
*permits integration with other data
Cons
*Compression/decompression takes time
*packet loss
*erros in transmission |
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Term
| VoIP Scenarios - Computer to Computer |
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Definition
| PC to router to Internet to router to PC |
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Term
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Definition
| PC to router to internet to gateway to PSTN and vice versa |
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Term
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Definition
| PSTN to gateway (via IP backbone to nearest gateway to the receiver) then via PSTN |
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