Question

What are the difference between WLAN and Cellular network? Name all available WLAN protocols in Data Networking

i. What is CSMA/CA in WLAN and how it works?

ii. Describe CSMA/CA technique that leverage DIFs, SIFs, and ACK.

iii. Describe CSMA/CA that uses RTS and CTS frames b . Describe the wireless evolution steps starting from 2G to LTE ( 1 paragraph)

c. What are the purposes of VLR and HLR in wireless network. What elements in mobile IP are similar to the H.R and VLR?

e. How VLR and HLR are used in wireless mobility.

Answer 1

Answer:-

difference between WLAN and cellular network

1, WIFI network:

Wi-Fi is a wireless technology that can connect various terminals to each other wirelessly, at rates up to several megabytes or even 1G. Wifi is public, such as their own home at a wireless router can have a small wifi network. Because he is public, we are in use, so there will be interference, so the wifi power is generally small, generally around 10mW, range tens of hundreds of meters, interference will be less. Individual erection of the wifi is an antenna, erected enterprises may have more than a dozen antennas, operators set up hundreds of antennas can form a network. But wifi wide coverage of the network far worse than the mobile network.

2, cellular network:

Mobile network refers to the 2G, 3G, 4G networks, these networks use a proprietary frequency, and a dedicated operator to plan, optimize and operate, so his launch power is generally around 20W, but also do very well Of the interference isolation, a base station coverage can reach 3-5 km. The use of these networks requires a complete registration authentication and billing procedures.

in conclusion:

Wifi is a public network, free, high-speed, discontinuous coverage, WIFI network source can come from the mobile network. Mobile networks are proprietary networks that are not free and continuous

Name all available WLAN protocols in Data Networking:-

Types of WLAN Protocols

802.11a Protocol

Technology: This protocol employs Orthogonal Frequency Division Multiplexing (OFDM), which is a modulation scheme well suited for the office environment, since digital data can be transmitted wirelessly over multiple frequencies.

Operating Frequency and Speed: This protocol achieves data transfer speeds as high as 54Mbps within a 5GHz frequency range. While this frequency is high, signals travelling at the 801.11a frequency have difficulty penetrating walls and other obstructive objects.

Pros: Signal coverage is comparatively less than other standards.

Cons: It is fairly expensive to implement.

802.11b Protocol

Technology: This protocol employs the multiple access method known as Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) with Ethernet protocol.

Operating Frequency and Speed: It operates within the 2.4GHz range and supports 11Mbps bandwidth speed. Though this bandwidth is lower compared to 802.11a capacity, it greatly facilitates path sharing.

Pros: It is less vulnerable to obstructive interferences such as walls. Implementation is low-cost with a good data transmission signal.

Cons: 802.11b runs as the slowest maximum speed of 11Mbps compared to other protocols. Household appliances may cause interference with this protocol.

802.11g Protocol

Technology: The 802.11g protocol became the newest standard in the 802.11 family of protocols in 2002-2003. With 802.11g, a combination of characteristics from 802.11a and 802.11b are employed.

Operating Frequency and Speed: 802.11g supports both the 5GHz (802.11a standard) and 2.4GHz (802.11b standard) frequencies, which allows this protocol to operate at wider ranges with less vulnerability to obstructive objects. With these dual characteristics, 802.11g is backward compatible with 802.11b devices. This means that in their respective environments, their access points and network adaptors can work interchangeably. Communication nodes within the 802.11g environment can be reconfigured to run at the lower 11Mbps speeds.

Pros: 802.11g is characterized by high speeds, good signal range, and resilience to obstruction. It is also backward compatible with 802.11b

Cons: It is susceptible to household appliance interference if the signal frequency is not regulated correctly. It can also be more expensive to implement.

802.11n Protocol

Technology: The 802.11n protocol is a further improved addition to the 802.11 family of protocols. Also known as Wireless N, 802.11n is an upgrade of 802.11g. It makes use of Multiple Input/Multiple Output (MIMO) technology

i)ans

WhatIs.com

   

CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is a protocol for carrier transmission in 802.11 networks. Unlike CSMA/CD (Carrier Sense Multiple Access/Collision Detect) which deals with transmissions after a collision has occurred, CSMA/CA acts to prevent collisions before they happen.

In CSMA/CA, as soon as a node receives a packet that is to be sent, it checks to be sure the channel is clear (no other node is transmitting at the time). If the channel is clear, then the packet is sent. If the channel is not clear, the node waits for a randomly chosen period of time, and then checks again to see if the channel is clear. This period of time is called the backoff factor, and is counted down by a backoff counter. If the channel is clear when the backoff counter reaches zero, the node transmits the packet. If the channel is not clear when the backoff counter reaches zero, the backoff factor is set again, and the process is repeated.

ii)ans

Helps prevent data collisions
Avoids unnecessary data traffic with the RTS/CTS extension

If participants in a wireless network follow Carrier Sense Multiple Access with Collision Avoidance, certain steps must be adhered to. First, the stations monitor the transmission medium. When it comes to WLAN, this means that carrier sense monitors the radio channel and checks whether other network participants – as long as they are visible to the respective device – are currently transmitting.

III)ans

a)

CSMA/CA can optionally be supplemented by the exchange of a Request to Send (RTS) packet sent by the sender S, and a Clear to Send (CTS) packet sent by the intended receiver R. Thus alerting all nodes within range of the sender, receiver or both, to not transmit for the duration of the main transmission. This is known as the IEEE 802.11 RTS/CTS exchange. Implementation of RTS/CTS helps to partially solve the hidden node problem that is often found in wireless networking

b)ans

Cellular Communication Technology has evolved over the past 3 decades with each phase bringing with it new and exciting capabilities and services to the end user. It’s been more than a century since Graham Bell invented the Telephone. He would be incredibly surprised where we’ve gotten now with his initial ideas. Even more puzzling to him would be the fact that we now use not wired-line Telephones, but cordless mobile phones to communicate over long distances.Africa has been hailed for skipping the landline telephone era by rapidly adopting wireless cellular Technologies instead based on GSM (Global System for Mobile communication) standards instead. GSM standards include first Generation or 1G, then second Generation (2G) and then third Generation (3G). These standards can be hard to understand. But what’s important is to remember what services were supported with each technology and that’s what we’ll be looking at.

Cutting the cord with 1G and 2G

First-generation technology of the early 1980s—1G—was based on analog transmissions. 1G technology only provided voice and subscribers were super excited with the new mobile technology now that they didn’t have to rely on stationary telephones or landlines at home or in the office. For the first time, cellular technology had cut the cord from the telephone, giving users the flexibility of being mobile while still staying connected!

Then industry switched to digital spread spectrum about 10 years later, ushering in the age of 2G cellular networks based on Global System for Mobile Communication (GSM) standard. 2G came along with improved transmission quality, system capacity, and coverage for the telecoms and for the subscribers, encryption, voice, voicemail, SMS and basic data called General Packet Radio Service (GPRS). 2G cellular systems include GSM, digital AMPS (D-AMPS), code-division multiple access (CDMA), and personal digital communication (PDC).

The telecoms began to realize the potential in SMS after having been accidentally discovered it. By now, it had become another cash cow for the mobile operators, but data was far from enabling subscribers do anything useful on their handsets.

At only 114Kbps and with low-processor, small screen devices, mobile browsing was the most frustrating (remember the dark days of WAP) and expensive(yes MTN Uganda, I spent UGX 500 to download a 14KB .gif image for a wallpaper on my Motorola W220) thing anyone could attempt doing on their phone.

Even though it got a lot better with the release of 2.5G network that brought along with it EDGE(Enhanced Data rates for GSM Evolution), still at only about 256Kbps, using phones having more or less same capabilities as their predecessors wasn’t much of an improvement.

Fast forward to 3G

3G, short for 3rd Generation, is a term used to represent the 3rd generation of mobile telecommunications technology.The 3G technology adds multimedia facilities to 2G phones by allowing video, audio, and graphics applications to be transmitted over the network. 3G is like the puberty of mobile network standards. On 3G phones, you can stream video or have video telephony. The idea behind 3G is to have a single network standard instead of the different types adopted in the US, Europe, and Asia.

A 3G cell-phone system depends on code division multiple access (CDMA) and spread spectrum radio technology, which allows many users to share both time and frequencies. If eight units of bandwidth are available, for instance, each user can transmit all of the time over all of the frequencies, but will be limited to using only one of the eight available orthogonal codes (non-overlapping communication channels for each active link) to avoid interference with anyone using the other seven units of bandwidth. I know, that’s a bit hard to digest, but here’s the break down of the network standards based on feature support added.

1G: Only voice

2G: Voice + SMS + basic data (GPRS)

2.5G: Voice + SMS + a little faster data (EDGE)

3G: Voice + SMS + fast data (3G)

3.5G: All the above with faster data speeds at 7.5Mbps

3.75G: All the above with even more faster data speeds at 21Mbps

The 3G standard was released in 2001, but it wasn’t until 2008 that telecoms here in Uganda began upgrading their networks to 3G.

Airtel Uganda 3G Mobile partner screenshot

If you see UMTS(Universal Mobile Telecommunications System) for instance on Airtel Uganda modems, High Speed Downlink Packet Access (HSDPA), sometimes known as 3.5G seen on MTN Uganda Modems and W-CDMA (Wideband Code Division Multiple Access), please understand that those are all variants of 3G technology.
The evolution of mobile networks has been coupled with the advancement of mobile phone technology too, both on the software and hardware fronts. The advent of 3G, ushered in a new revolution in smart phone technology (though it can also be interpreted the other way round) with the Apple’s iPhone [then] leading the way.

Mobile subscribers don’t care what network their operator uses until they experience for themselves how fast (or slow) they can send emails, stream YouTube videos, read news, update their status on social networks.

3.5G, 3.75, 4G LTE and beyond

Today several operators in the country claim to support 3.75G which offers up to 21Mbps downstream speed. But other than these networks powering 3G capable phones, what’s more interesting is that 3G is being used as the internet access means on laptops and stand-alone desktops through 3G modems. This is so because of low cost of installation (only a modem with a SIM card is required) and ease of reloading data, plus of course wide coverage of 3G networks across the country.

4G LTE (Long Term Evolution) is set to be the next big thing after 3G. Next year, local networks here are rumored to launch their 4G networks. Now if you think 21Mbps on 3G+ is faster, then you won’t grasp how fast 4G’s 100Mbps will be. That will mean, Youtube videos won’t buffer (seriously this time), downloading and updating your operating system won’t take as much time as it takes now. But 4G, will require that you’ve a 4G supported smartphone or 4G USB modem first also.

It’s self-evident that Africa leap-leapfrogged most of the wired technology and embraced wireless methods of communication. Wired networks like fiber are mostly used by the carriers as part of their core network or as a back-haul for their Microwave links but not as the last-mile solution to the subscriber. Put simply, the networks use fibre networks or microwave links to transfer large data between those red and white masts that finally deliver internet to your phone.

The quest for faster data links propagated by data-hungry web and mobile applications is pushing carriers to deploy wider data pipes. But this has to simultaneously be followed up by lower costs of data if carriers dream of mobile subscribers using their services

c)ans

Home Location Register (HLR) The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network. The HLR is an integral component of CDMA (code division multiple access), TDMA (time division multiple access), and GSM (Global System for Mobile communications) networks.

The primary role of the VLR is to minimize the number of queries that MSCs have to make to the home location register (HLR), which holds permanent data regarding the cellular network's subscribers

Additionally each interface between the different elements of the GSM network is also defined. ... the channels, timeslots and the like to be allocated to the mobile equipments ... B interface The B interface exists between the MSC and the VLR . ... the MSC the SMS-G. It transfers short messages and uses the MAP/H protocol.

e)ans

GSM networks use a two-level hierarchy of databases to manage mobility and assist with security. The Visitor Loca- tion Register (VLR) is a database located in the area serving the mobile device. It maintains a temporary profile for the mobiledevice. ... GPRS re-uses the GSM VLR/HLR databases for roaming and security.

HLR and VLR are are generally a register where they store data of subscribers or customers.

They store data like your IMEI no,location,handset,services(free call,low rate ,etc) enabled in your device. HLR and VLR also Authenticate your no too.They store these to make your call smoothly and fast.

HLR and VLR are connected to MSC(Mobile Switching Station) when your call to any no after reach to MSC . MSC ask from HLR and VLR for the data and authentication. When MSC receive response from them then MSC route call further call flow