Wimax And 3g Lte Technology Computer Science Essay


Dijkstras algorithm and Bellman-Fords algorithm deal the same with the shortest problem solving for a single source. Apparently, Dijkstra's algorithm's problem is that; it cannot handle the negative edge lengths, since the handling of negative lengths and shortest possible lengths between nodes is not noticed in dijkstra's algorithm; we have chosen the one that can handle the negative edge lengths. Since from the answer it is clearly visible that, the answers were of same, the negative edge path has no affect on answer obtained from Bellman-Ford and Dijkstra's algorithm.

These algorithms are used to solve the single source shortest path problem. But the main difference between these two algorithms is : that the Dijkstra's algorithm cannot deal with the negative edge lengths. But Bellman-Ford's algorithm can deal with the edges having negative lengths and the shortest path given by the each algorithm will not be the same. In this example there is no negative path so the answer is same.


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You are working for a technology consultancy and your client has requested a written technical briefing comparing WiMax and 3G LTE technologies. Write this brief in no more than 1 side of A4. You should begin by providing an overview of each technology and then critically discuss the advantages and disadvantages and say how you see each technology evolving over the next 5 years?



WiMax needs no special emphasis in the communication technology. IEEE; Institute of Electrical and Electronics Engineers association formed to look after the technology has promoted the WiMax; some says Wireless Maximum, taking the local coverage range to the broader area. With the WiMax installed the mobility and flexibility to the users will be dramatically increased. WiMax makes use of OFDMA to transmit the data in uplink and downlink wards. Mobile WiMax uses the IP backbones to sustain the network performance and operational procedures. WiMax is currently being deployed around the world and offering varied services which was reputing the technology. It is no doubt that, some day the WiMax will rule the communication world.

The WiMax derived from IEEE family of protocol. WiMax spread the wireless access from the local area network to metropolitan area network and wide area network. It will use the physical layer access technology i.e. called OFDMA for both of uplink and downlink channels. The 802.16-04 or802.16d is called the mobile WiMax. Mobile WiMax uses all IP backbone networks for support of uplink and downlink peak data rate competences. WiMax is developing to accomplish the global acceptance by working with regulators to promote global coordination of "WiMax friendly" spectrum. Mobile WiMax is adopted by the ITU and hence the chance to become the next generation wireless internet access leader.

What is LTE Technology?

LTE is the latest innovation from the communication engineers. It is still under the full-testing conditions but is expected to beat the offerings promoted by the WiMax technology. LTE is the idea relied on WCDMA; Wireless Code Division Multiple Access. E-UTRA and E-UTRAN; UMTS Terrestrial Radio Access and UMTS Terrestrial Radio Access Network are the specifications proposed by the 3GPP association. 3GPP released the LTE technology in the release 8. The uplink and downlink channels usage to transmit the data is different to WiMax; Uplink uses the SC-FDMA, and Downlink uses the OFDMA.

The LTE is new technologies that derived from the third generation technology which is based on WCDMA. The specifications of the feasibility study by 3GPP efforts are formally known as the evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS terrestrial radio access network (E-UTRAN).The first version of LTE is documented in Rel.8 of the 3GPP specifications. Which define a new physical layer radio access technology which is based on (OFDMA) for the downlink and fixed WiMax. Similar in concept to the SC-FDMA for the uplink channel.

Advantages of WiMax technology:

1) 100's if users can be accommodated with a single access point/station 

2) Quick convergence of new users and much flexibility

3) Can attain 10Mbps for up-to 10 kms, when the line-of-sight is noticed. 

4) Standards have been set and no problem with the conflicting standards and frequencies.

Disadvantages of WiMax technology:

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1) Line-of-Sight is essential, for longer distances.

2) Rain and bad weather has adverse effects on the signal strength and quality.

3) Interference from the other wireless devices. 

4) Power consuming and special electrical installments are needed.

Advantage of 3G LTE technology:

Faster in speed and data rates. Can attain 100Mbps and 50Mbps, download and upload respectively.

The most admirable advantage is GSM/CDMA gap can be settled down with the LTE

LTE has lower latency that can suffice the real-time applications on mobile.

Disadvantages of 3G LTE technology:

LTE should start afresh.

LTE radio channel selection and interface medium is yet to chosen and under developing.

No standard device is released yet.

No service and testing success stories available yet.

Technical Specification of both Technologies:

Future Trends for both technologies over next 5 years:

Mobile WiMax and LTE, both can be proclaimed as the future communication technology. The LTE and WiMax uses the OFDMA for Downlink channel to attain the highest data transfer between end parties. MIMO antenna solutions can be applied to both LTE and WiMax. It is acceptable for any technology to invest for an up gradation from 3G network to concerned Mobile WiMax and LTE.

Mobile WiMax and LTE are both accepted as candidates to meet IMT-Advanced performance goals. Both of technologies Mobile WiMax Rel 1.5 and LTE have comparable performance. WiMax and LTE both of use OFDMA in the DL with higher order modulation. Both support higher order MIMO antenna solutions. Comparable investment to upgrade 2G/3G network to LTE or Mobile WiMax.


For the bit stream 001010, sketch the waveform for bipolar-AMI, differential Manchester, NRZL, and NRZI ?





Differential Manchester Coding


A PCM encoder accepts a signal with a full-scale voltage of 12V and generates 12-bit codes using uniform quantization. The maximum normalized quantized voltage is 1-2-12. Determine

a. Normalized step size

b. Actual step size in volts

c. Actual maximum quantized level in volts

d. Normalised resolution

e. Actual resolution

f. Percentage resolution


Given data is :

Voltage: 12v

Code: 12-bit

Max Normalization quantized voltage: 1-

Normalized step size

= 0.000244

Actual step size in volts

12x = 0.00024x12=0.00292 v

Actual maximum quantized level in volts

[1-(1\4096)]12 = 11.99 v

Normalised resolution

(1/2) = 0.000122

Actual resolution

0.00012 12 = 0.0014 v

Percentage resolution

(1/2) x x 100 = 0.012%


Consider the use of 1000-bit frames on a 1-Mbps satellite channel with a 300-ms delay. What is the maximum link utilization for

a. Stop-and-wait flow control?

b. Continuous flow control with a window size of 7?

c. Continuous flow control with a window size of 127?

d. Continuous flow control with a window size of 255?


Given data

Frame=1000 bit

Satellite channel=1-MBPS

Delay=300 ms

Stop-and-wait flow control

We use this formula to find the link utilization of link.



1000/ = 1/601


For window size of 7

= 7/601

For window size of 127

= 127/601

For window size of 255

= 255/601


Two neighbouring nodes (A and B) use a sliding window protocol with a 3-bit sequence number. At the ARQ mechanism, GO-back- is used with a window size of 5. Assuming A is transmitting and B is receiving, show the window position for the following succession of events:

a. Before A sends any frames

b. After A sends frames 0, 1, 2 and 3 and B acknowledges, 0, 1 and the Acks are received by A.

c. After A sends frames 3, 4, 5 and B acknowledges, 4 and the Acks are received by A.


Sliding window protocol= 3 bit

Window size= 5



What is the bandwidth efficiency for FSK, ASK, PSK and QPSK for a bit error-rate of 10-8 on a channel with S/N of 14 dB?


Bit error rate=

S/N= 14db

For FSK and ASK

Eb/No = S/N-(R/B¬t) dB

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From graph Eb/No=14.6 db

(R/B¬t) dB=-0.6db



11.6db=14bd-(R/B¬t) dB

(R/B¬t) dB=-2.4db


For QPSK we take into the baud rate D=R/2



An operator of a cellular mobile system has selected a transmission system which requires a carrier-to co-channel interference ratio of at least 19 dB. How many cells per cluster are required to satisfy the carrier-to co-channel interference requirement? State all assumptions made in your calculations?


Carrier to co-channel interference ratio=19db

C/I = 19 db

Assuming the propagation constant i=4

= 1/{6}


= 4.67

D/R =

N = 7.5


Evaluate three different routing protocols and provide a valid application of each ?


Routing is the way to direct packets or data across a network. It is a set of protocols implemented to make the network function better and optimized. Routing protocols uses the algorithms to find the shortest or best possible routes to direct the data across the network.

Routing protocols are used for the implementation of routing information in software or hardware. Any routing protocol uses the matrices to find the actual path to transmit a packet of data across the network.

Types of Routing Protocol

Exterior Routing Protocols

Interior Routing Protocols

Hybrid Routing Protocol

Interior vs. Exterior Routing Protocols

Protocols that work within the organisation are called interior routing protocols and are meant to function in the organisation particularly. Exterior routing protocols that work between the two or different multiple organisations are called exterior routing protocols.

OSPF; Open Shortest Path First is IGP; Interior Gateway Protocol. Alterntive noticed IGP protocols were: IS-IS, RIP, and EIGRP.

BGP; Border Gateway Protocol is Exterior Gateway Protocol. Only BGP is used as the exterior routing protocol. BGP is seen in internet operating servers and DNS servers working at different organisations and regions, which are responsible to maintain the route and network.


EIGRP is the proprietary protocol of CISCO. EIGRP is seen only in cisco routers. EIGRP uses a maximum hop of 255 counts. EIGRP is not an open source protocol and hence the other routing devices do not use the EIGRP; instead use OSPF protocol for routing functions. The best shortest path selection is done by the EIGRP protocol. VLSM and hop count support can be seen in EIGRP protocol. EIGRP has both characteristics of link state and distance vector types.


A single admin device uses the EIGRP protocol. Only CISCO devices implement the EIGRP protocol. If a network contains mixed proprietary routers, the EIGRP usage cannot be implemented.


OSPF is the Open Shortest Path First protocol. It is link state routing protocol. OSPF can be used in any routing devices, since the open protocol standard, the deployment of protocol is easy and flexible to the network administrators. The frequent information sending to the neighbours to share the network information is done by the OSPF protocol. The OSPF enabled router will send frequent HI messages to the devices connected in the network having the information of the device and subnet mask, network id router id and network location and all, if a reply is received from the router, it will expect it to be a neighbour router.


Used within organisations. Open Shortest Path First is open standard, so used in any vendor device.


BGP; Border Gateway Protocol is the only exterior gateway routing protocol running the internet. BGP functions on the top of the internet, coordinating the different vendor devices or networks to function together. BGP uses the AS number particularly to route the data across the network. Any company having the BGP router enabled device, can be assigned with the AS number and function. BGP maintains a routing table containing the IP address of destination and next hop. BGP is capable to filter unwanted broadcasts, to mitigate the load on routers.


Used in internet backbone routers.