# Mobile Networks

This topic page is for organizing the development of content related to wireless systems.
If you are knowledgeable in any area Wireless systems, feel free to improve upon what you see, we would greatly appreciate your contributions.

## Introduction

Wireless networks have significantly impacted the world as far back as World War II. With the use of wireless networks, information could be sent overseas or behind enemy lines easily and quickly and was more reliable. Since then wireless networks have continued to develop and its uses have significantly grown. Cellular phones are part of huge wireless network systems. People use these phones daily to communicate with one another.
Sending information over seas is only possible through wireless network systems using satellites and other signals to communicate across the world otherwise getting information Emergency services such as the police department utilize wireless networks to communicate important information quickly. People and businesses use wireless networks to send and share data quickly whether it be in a small office building or across the world. Another important use for wireless networks is as an inexpensive and rapid way to be connected to the Internet in countries and regions where the telecom infrastructure is poor or there is a lack of resources, like most Developing Countries.
Wireless networks allow you to eliminate messy cables. Wireless connections offer more mobility, the downside is there can sometimes be interference that might block the radio signals from passing through. One way to avoid this is by putting the source of your wireless connection in a place where the signal will have as little interference as possible. Sometimes nearby networks are using the same frequencies, this can also cause interference within the network and can reduce its performance.
Compatibility issues also arise when dealing with wireless networks. Different components not made by the same company may not work together, or might require extra work to fix compatibility issues. To avoid this, purchase products made by the same company so that there are fewer compatibility issues.
Wireless networks, in terms of internet connections, are typically slower than those that are directly connected through an Ethernet cable. Though the speed is slower, most things will still move at the same speed except for things like video downloads. Though wireless technology continues to develop, it is now easier to get networks up and running cheaper and faster than ever before.
A wireless network is more vulnerable because anyone can try to break into a network broadcasting a signal. Many networks offer WEP - Wired Equivalent Privacy - security systems which have been found to be vulnerable to intrusion. Though WEP does block some intruders, the security problems have caused some businesses to stick with wired networks until security can be improved. Another type of security for wireless networks is WPA - Wi-Fi Protected Access. WPA provides more security to wireless networks than a WEP security set up. The use of firewalls will help with security breaches which can help to fix security problems in some wireless networks that are more vulnerable.
Wireless networking can entail a number of technologies. Some are listed below.

## Bluetooth

Typically used to create Personal Area Networks (PANs), Bluetooth has a distance limitation of up to 100 meters. The Bluetooth standard defines 3 classes of transmitters and receivers.
* Class 1 defines a maximum permitted power of 100mW (20 dBm) and can transmit up to approximately 100 meters.
* Class 2 defines a maximum permitted power of 2.5mW (4 dBm) and can transmit up to approximately 10 meters.
* Class 3 defines a maximum permitted power of 1mW (0 dBm) and can transmit up to approximately 1 meter.

## IEEE 802.11

As described in Network communication medium, IEEE 802.11 refers to the standards of wireless technology most commonly used today in network connections.
The current standard for this the IEEE 802.11x standards also called Wi-Fi for Wireless Fidelity. Wi-Fi is being used by both business and consumer as a way to share a internet connection as well as P2P connections. Currently there are three Wi-Fi Standards a, b and g, the n and i standards are currently being developed.
802.11b - 802.11b was the first wi-fi standard to be introduced and has a maximum speed of 11Mbps.
802.11a - 802.11a was the second wi-fi standard and had a maximum speed of 54Mbps with the same range transmission and is not compatible with 802.11b because it used the 5GHz band and which has less interference.
802.11g - 802.11g was the third standard and had a maximum speed of 54Mbps and much farther range than both a and b but is backward compatible with 802.11b.

## Security

* Wired Equivalent Privacy (WEP)
* Wi-Fi Protected Access (WPA)
* Wi-Fi Protected Access Version 2 (WPA2)
* 802.1x

## Further introduction

Today being able to connect with the world while you are on the go is a natural habit by virtue of mobile networks and services you enjoy from service providers of GSM 2G, CDMA, WCDMA or 3G/UMTS and or HSPA. A few of us may be already using LTE or 4G devices for data connectivity already.What makes your user equipment work?, how are you able to talk to others as easily as you could on your plain old telephone system of PSTN? In this introductory discussion on mobile networks you can obtain answers to such questions.
Way back during 1980s, world has seen Advanced Mobile Phone Systems in the USA and primitive GSM networks emerged in Europe. The notion of cellular mobile communications emerged with studies performed by Bell Labs and conserted efforts of EU like strong bodies to make it a sustainable globally roaming friendly wireless communication system that is in practice still after more than three decades since its inception. While North American region has welcomed all emerging wireless technologies and standards to be incorporated in their nations, Europe predominantly retained strong affiliations with Groupe Spaciale mobile or GSM standard and its data versions such as GPRS, EDGE. 3GPP and 3GPP2 partnership projects have emerged giving a sense of project managerial support to promote standards and currently we have Release 15 being updated during 2014 June time frame as we read this article
From a 200 khz base band as used in GSM full duplex at 900 mhz range of spectrum, CDMA evolved as 1.23 mhz spectrum with a distictly different wireless paradigm of unique codes being used for users,Base Station, Mobile device networking elements and traffic channels. UMTS emerged as a wideband version of CDMA with a typical 5 Mhz bandwidth to cater for both voice and data requirements as per IMT2000 guidelines of ITU-R. With the advent of Orthogonal Frequency Division Multiplexing concepts from Wavelan of AT&T, primitive implementations of 1.4 mhz LTE have emerged during 2008 especially after WiMAX standard of IEEE 802.16 has started not being able to overcome Peak to Average Power Ratio issue in the uplink. Thus the wirless LTE uplink now uses SC-FDMA standard with 15 khz sub carriers. A Resource Block in LTE is a spectrum entity of 12 times 15000 hz sinusoidal waves that makes 180 khz just almost similar in size of a radio transeiver or RT with big boost in terms of being able to generate seven symbols per a slot on each and every sub carrier yielding two chunks of 84 resource elements per a milli second Thus with 20 Mhz spectrum allocation of LTE one gets a hundred resource blocks and 100.8 megabits per second throughput in the downlink.This can be accumulated upto 300 megabits per second using 4T4R MIMO. An advanced implementation of the same technology with Coordinated Multipoint and Carrier Aggregation can take the datarate to as high as 1 gbps and beyond as 3 gbps with 100 mhz spectrum allocation and coordinated beam forming of nearby eNodeBs towards the target UE to make such a huge data rate possible

## Learning resources

A good beginning is ftp://ftp.3gpp.org Specs Year 2010 Dec for instance Chose Release 8 or above Pick up a maiden document such as 36.300 Subsequently as you delve deeper on a specific subject such as PHY layer, you might want to download specs 36.211,36.212.36.213 or 36.214

## Wikipedia

* Ralink