Communication

Mobile Communication

mobile communication

Mobile Phone:

A mobile phone (also known as a cellular phone, cell phone, hand phone, or simply a phone) .

It is a phone  that can make and receive signal  over a RF while moving around a wide geographic area.

It does so by connecting to a network provided by a phone, allowing access to the network By contrast, a wireless phone is used only within the short range of a single, private base station.

Cellular Mobile Systems

Goals:

  • High capacity
  • Large coverage area
  • Efficient use of limited spectrum

Cellular technology supports geographically mobile users, which is not possible in hard-wired network.

Cellular Systems accommodate a large number of users over a large geographic area, within a limited frequency spectrum.

In cellular networks, the distance between a transmitter and a receiver is unpredictable because it depends on the location of the users. However, cellular telephone systems provide high quality service that is often comparable to that of the land-line telephone systems.

Cellular Concepts

Replacing a single, high power transmitter with many low power transmitters, each providing coverage to only a small area.

Neighboring cells are assigned different groups of channels in order to minimize interference.

The same set of channels is then reused at different geographical locations.

Cells labeled with the same letter use the same group of channels.

Cell Cluster: group of N cells using complete set of available channels Many base stations, lower power, and shorter towers

Small coverage areas called “cells”

Each cell allocated a % of the total number of available channels

Hexagonal cell shape assumed for planning simple model for easy analysis circles leave gaps

cell center omni-directional antenna (360° coverage)

Handover / Handoff

When a mobile user travels from one area of coverage or cell to another cell within a call’s duration the call should be transferred to the new cell’s base station. Otherwise, the call will be dropped because the link with the current base station becomes too weak as the mobile recedes. Indeed, this ability for transference is a design matter in mobile cellular system design and is call handoff.

Global System for Mobile:

GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second-generation (2G) digital cellular networks used by mobile phones. As of 2014 it has become the default global standard for mobile communications – with over 90% market share, operating in over 219 countries and territories.

2G networks developed as a replacement for first generation (1G) analog cellular networks, and the GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony. This expanded over time to include data communications, first by circuit-switched transport, then by packet data transport via GPRS (General Packet Radio Services) and EDGE (Enhanced Data rates for GSM Evolution or EGPRS).

 

GSM Architecture

SIM  –   Subscriber Identification Module.
MS   –   Mobile Station.
ME   –   Mobile Equipment.
BTS   –   Bare Transceiver System.
MSC   –   Mobile Services switching Center.
NSS   –   Network & Switching Subsystem.
PSTN   –  Public Switched Telephone Network.

General Packet Radio Service

General packet radio service (GPRS) is a packet oriented mobile data service on the 2G and 3G cellular communication system’s global system for mobile communications (GSM). GPRS was originally standardized by European Telecommunications Standards Institute (ETSI)

 

GPRS is a best-effort service, implying variable throughput and latency that depend on the number of other users sharing the service concurrently, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection. In 2G systems, GPRS provides data rates of 56–114 kbit/second. 2G cellular technology combined with GPRS is sometimes described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate-speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system. GPRS is integrated into GSM Release 97 and newer release.

Advantages of GPRS

SMS messaging and broadcasting

“Always on” internet access

Multimedia messaging service (MMS)

Push to talk over cellular (PoC)

Instant messaging and presence—wireless village

Internet applications for smart devices through wireless application protocol (WAP)

Point-to-point (P2P) service: inter-networking with the Internet (IP)

Point-to-Multipoint (P2M) service

point-to-multipoint multicast and point-to-multipoint group calls

GPRS Architecture

  • SGSN (Serving GPRS Support Node).
  • GGSN (Gateway GPRS Support Node)

ZigBee

‘ZigBee’ comes from the honeybees. The honeybees dance in the Zig-Zag pattern, sharing information such as the location, distance, and the amount of a discovered food source to the other fellow members.

ZigBee is a specification for a suite of high-level communication protocols used to create personal area networks built from small, low-power digital radios.

The technology defined by the ZigBee specification is intended to be simpler and less expensive than other wireless personal area networks (WPANs), such as Bluetooth or Wi-Fi.

ZigBee data transmission rate varies from 20 to 900kbits.

 

ZigBee Applications

  • Wireless sensor networks
  • Industrial control
  • Embedded sensing
  • Medical data collection
  • Smoke and intruder warning
  • Building automation

 

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