WILAN 14

WILAN 14

List the different WiFi frequency bands and their associated names/standards. Explain how to increase WiFi coverage using different technologies and what security solutions exist to ensure confidentiality.

Your operator has delivered you a binary software image, viewed with a hex editor, coming from a CPU you are not familiar with. She states that it was from a RISC 32 bit architecture that is commonly used in many devices. What steps would you take to identify the image? Be as specific as possible. What follows on questions would you ask to facilitate your analysis?

RISC -Reduced Instruction Set Computer is used in portable devices due to its power efficiency. It is a type of microprocessor architecture that uses a highly-optimised set of instructions. The design of a 32-bit data width Reduced Set Instruction Computer (RISC) processor was developed with simplicity and implementation efficiency. It has a complete instruction set, program and data memories, general purpose registers and a simple arithmetic logical unit (ALU) for basic operations.

To identify the given image is RISC process, the below system diagram will help.

The system architecture of a 32 – bit RISC processor:

The RISC processor architecture consists of

Arithmetic Logic Unit (ALU)

Control Unit (CU)

Barrel Shifter

Booth’s Multiplier

Register File and Accumulator.

RISC processor is designed with load/store architecture, means that all operations are performed on operands held in the processor registers, and the main memory can only be accessed through the load and store instructions.

For increasing the speed of operation, the RISC processor is designed with five stage pipelining. The pipelining stages are

Instruction Fetch (IF),

Instruction Decode (ID),

Execution (EX),

Data Memory (MEM), and

Write Back (WB)

Instruction fetch: It is used to obtain a directive from the instruction memory using the current value of the PC and increment the PC value for the next instruction.

Instruction Decode: It uses the 32-bit instruction provided from the previous instruction fetch unit to index the register file and obtain the register data values. The instructions opcode field bits [31-26] are sent to a control unit to determine the type of instruction to execute.

Execution: The type of instruction then determines which control signals are to be asserted and what function the ALU is to perform, thus decoding the instruction. The register file reads in the requested addresses and outputs the data values contained in these registers. These data values can then be operated on by the ALU whose operation is determined by the control unit to either compute a memory address (e.g. load or store), compute an arithmetic result or perform a compare.

Data memory: The control unit has two instruction decoders that decode the instruction bits and the decoded output of the control unit is fed as control signal either into Arithmetic logic unit (ALU) or Barrel shifter or Booth’s Multiplier. If the instruction decoded is arithmetic, the ALU result must be written to a register. If the instruction decoded is a load or a store, the ALU result is then used to address the data memory.

Write Back: finally, it writes the ALU result or memory value back to the register file.

MODULES DESIGN OF 32 – BIT RISC PROCESSOR

The modules of the RISC processor are

Control Unit (CU)

ALU

barrel shifter

Booth’s Multiplier and

General Purpose Registers.

Control Unit The control unit of the RISC processor examines the instruction opcode bits [31 – 26] and decodes the instruction to generate nine control signals to be used in the additional modules as Arithmetic Logic Unit (ALU): It executes all arithmetic and logical operations. The arithmetic/logic unit can perform arithmetic operations or mathematical calculations like addition, and subtraction. As its name implies, the arithmetic/logic unit also performs logical activities include Boolean comparisons, such as AND, OR, XOR, NAND, NOR and NOT operations

Barrel Shifter: It consists of a total of eight 8×1 multiplexers. The output of one multiplexer is connected as an input to the next multiplexer in such a way that the input data gets shifted in each multiplexer, thus performing the rotation operation. Depending on the select lines, the number of rotation varies. With select lines low, there is no output. If select line c0 is high, 1-bit rotation takes place, if c1 is high 3-bit rotation.

Booth’s Multiplier The Multiplier is implemented using the modified Booth algorithm. The two main advantages of this algorithm are speed and the ability to do signed multiplication (using two’s complement) without any extra conversions. It uses an extra bit on the right of the least significant bit in the product register.

General Purpose Register The eight-bit input data is stored in this register. This register acts as a source register. The register file has two reads and one writes input ports, meaning that during one clock cycle, the processor must be able to read two independent data values and write a separate value into the register file. The register file was implemented in VHDL by declaring it as a one-dimensional array of 32 elements or registers each 8-bit wide. It consists of eight D – flip flops and eight AND gates.

The questions to ask if the image is 32-bit RISC processor not:

Does the image has the following features

1. Load/store architecture- means it should fetch operands and results indirectly from the main memory through a lot of scalar registers.
2. Fixed length instructions: which means whether it more comfortable with decoding than variable length instructions, and use fast, inexpensive memory to execute a larger piece of code.
3. Hardwired controller instructions: This is where RISC shines as hardware implementation of guidelines is much faster and uses less silicon real estate than a microsite area.
4. Fused or compound instructions which are heavily optimized for the most commonly used functions.
5. Pipelined implementations with the goal of executing one instruction (or more) per machine cycle.
6. The large uniform register set
7. Minimal number of addressing modes
8. no/minimal support for misaligned accesses

Introduction

The measurement and analysis of radio waves are critical today [1]. It plays a significant part and plan of WLAN applications. Wi-fi is widely used globally today. Due to its effectiveness, it has emerged to be widely used.

For this reason, it is easy to send and receive information very fast. A fundamental component where Wi-fi is composed is the access points and the mobile clients. For wireless networks, Access Points (APs) are positioned at different places in an environment. They can be held within an organization as well as from outdoor sources. Mobile clients usually communicate with each other by first communicating with the access points from where they are able to access the outside world.

A major principle witnessed in Wi-fi is that data is normally transmitted in form of electromagnetic waves. A radio wave travels from one device to another [1]. In the process, there are different hinderances that impact the signal strength. Radio signal often passes through various obstacles such as glass, wood, a concrete. In the presence of such obstacles, often there is a reflection, diffraction, and scattering. Scattering, for example, makes the signal weak when it reflects over rough surfaces. Therefore, some few aspects affect the strength of the signal. The paper analyzes some of the major aspects that impact Wi-fi’s signal strength. Most of the obstacles as it will be seen are mostly in physical form. However, other obstacles interfere with the strength as well.

Wi-fi Interference

WI-FI signal is measured in radio waves. Access Points are provided at different locations to connect to WI-FI signals. They offer fast communication between clients. Data is normally transmitted between these APs in electromagnetic waves [5]. This is where radio waves move from one device to another. Mostly, there are obstacles in which these radio waves pass through. These aspects affect the signal’s strength. Interference comes from within WI-FI sources as well as from non-WI-FI sources. Different obstacles exist that interfere with WI-FI signals. Most of these obstacles remain unknown while others are common.

Most of the complaints from IT admins come from interference. Interference normally occurs in a wireless network when a signal is disrupted. This normally causes a kind of degradation of the wireless network. In most cases, a weak signal is not reliable [2]. For most organizations, they use wireless networks to increase the efficiency of communication. Different classes of interference normally exist today. They are namely non-Wi-Fi sources and from within the Wi-Fi sources. Of the two, Wi-Fi sources are often more discussed and widely known. Wi-fi sources are easy to control in many aspects. Therefore, an interference will come from the two identified sources in many cases.

Most of the wireless networks and equipment are normally subjected to IEEE standards [6]. These standards normally identify and describe all specifications and requirements when configuring Wi-Fi networks. IEEE standards attempt to describe all the layers in a wireless network. Therefore, different standards are utilized to ensure that wireless networks function appropriately. Most of the wireless networks rely on 802.11b/g standard. It involves a measurement of the signal strength as well. Despite having different standards in existence today, Wi-fi interference is common for many enterprises. Having the right standards is not an assurance that there will lack interference [1]. Mostly, a wireless network will be effective where obstacles are minimal.

Interferences of Wi-Fi

WI-FI interference is common today [6]. They often lead to a weakening of signals making it unreliable. Interference is hard to evade in most cases. This is because of these obstacles exist in real world and they are not easily evaded. Also, others are within us and users have to cope with the fact that they exist.

From different reviews, various obstacles exist that block signals from being strong. Most of the interferences are non-Wi-Fi while others are within the Wi-Fi networks. Many of the obstacles are widely known while others aren’t known. Also, it is clear that these obstacles present their different degrees of impact [2]. Wireless interference is important consideration when planning for this kind of connection. Interferences today are severed and most of them are inevitable. A major challenge comes when trying to minimize such interferences. Wireless networks rely on the effectiveness of radio frequencies [6]. It should be in a clear and unobstructed environment for it to be effective. The following are the major interferences of wi-fi signals.

Physical Objects: They present a high percentage of an overall wi-fi interference. They include trees, masonry, buildings and other structures. It is clear that the density of such materials poses a different degree of threat. At some point, radio frequencies are able to pass through some of these objects. However, with a high density, it is often difficult for such signals to remain strong [4]. Other objects such as steel and concrete make it impossible for the signals to pass completely. Wireless signals are weakened and even some don’t work from these structures.

Radio Frequency Interference: Wireless technologies such as 802.11b/g use a radio frequency that ranges from 2.4GHz. Using the same channel can cause radio frequency interference. Such interferences include noise that weakens radio signal. Thus, such interferences cause the wireless signals to become inappropriate.

Electrical Interference: This kind of interference normally comes from electronics such as computing devices, lighting equipment, and other motorized devices. An impact posed by an electrical interference depends on the proximity of the electronic device. With recent advances in wireless technologies, this kind of interference is being reduced in a great manner. Despite such improvements, such electronics play a huge role in different kinds of interferences.

Environmental Factors: Different environmental factors also impact the strength of the signal. Weather conditions play a critical role in this kind of interference. Lightning causes signals to weaken as it produces electromagnetic waves that act against WI-FI strength. Mist and fog makes it difficult for signals to pass very fast [2]. Therefore, adverse weather conditions will affect the effectiveness of an electric signal.

Enterprise networks consist of various networking equipment. Most of them are not aware of the interferences they are exposed to. Wireless Fidelity router is one important component that allows this connection. A router allows this as it ensures that data is routed from one or multiple hubs. WI-FI is evolving and it is not a new technology today. More so, this technology operates through electromagnetic means. Thus, in one way or another, they are susceptible to different interferences.

From an overview of all these aspects, wireless signals will always be impacted. Therefore, before setting up this network, it is important to understand all the critical factors that could impact the strength of a signal.

REFERENCES

[1]

2011. Mangir, S. Lelass and H. Younan , “Analyzing the Impact of Wi-Fi Interference on,” International Journal of Distributed and Parallel S, vol. 2, no. 4, 2011.

[2]

2014. Kaur, “Bluetooth and Wi-fi Interferences: Simulations and Solutions,” International Journal of Advanced Research in Computer and Communication Engineering, vol. 3, no. 9, 2014.

[3]

2015. Nagarajan and R. Dhanasekaran, “Analysing The Effect Of Interference in Wireless Industrial Automation Systems,” ARPN Journal of Engineering and Applied Sciences, vol. 10, no. 6, 2015.

[4]

2013. Sohail, Z. Ahmad and I. Ali, “Analysis and Measurement of Wi-Fi Signals in Indoor Environment,” International Journal of Advances in Engineering & Technology,, 2013.

[5]

Rabbit, “An Introduction to Wi-Fi,” Rabit and Dynamic, 2008.

[6]

2009. Harwood, “Wireless Networking,” Pearson, 9 July 2009. [Online]. Available: http://www.pearsonitcertification.com/articles/article.aspx?p=1329709&seqNum=3. [Accessed 31 October 2017].