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Data And Computer Communications 10th Edition William Stallings - Solutions
What is refraction?
What is the primary cause of signal loss in satellite communications?
What factors determine antenna gain?
What is the advantage of a parabolic reflective antenna?
What is an isotropic antenna?
What two functions are performed by an antenna?
Indicate some significant differences between broadcast radio and microwave.
Why must a satellite have distinct uplink and downlink frequencies?
What is direct broadcast satellite (DBS)?
What are some major advantages and disadvantages of microwave transmission?
What is the difference between unshielded twisted pair and shielded twisted pair?
What are some major limitations of twisted-pair wire?
Why are the wires twisted in twisted-pair copper wire?
An amplifier has an output of 20 W. What is its output in dBW?
If an amplifier has a 30-dB voltage gain, what voltage ratio does the gain represent?
Fill in the missing elements in the following table of approximate power ratios for various dB levels. Decibels 1 2 3 4 5 Losses Gains 0.5 2 9 7 8 9 10 0.1 10
In a 1939 letter to Vannevar Bush, Claude Shannon said he was working on a theorem, which states that for any transmitter and receiver the length of an arbitrary message multiplied by its essential spectrum and divided by the distortion of the system is less than a certain constant times the time
If the received signal level for a particular digital system is -151 dBW and the receiver system effective noise temperature is 1500 K, what is Eb/N0 for a link transmitting 2400 bps?
The square wave of Figure 3.7c, with T = 1 ms, is passed through a lowpass filter that passes frequencies up to 8 kHz with no attenuation.a. Find the power in the output waveform.b. Assuming that at the filter input there is a thermal noise voltage with N0 = 0.1 mW/Hz, find the output
Given a channel with an intended capacity of 20 Mbps, the bandwidth of the channel is 3 MHz. Assuming white thermal noise, what signal-to-noise ratio is required to achieve this capacity?
Consider a channel with a 1 MHz capacity and an SNR of 63.a. What is the upper limit to the data rate that the channel can carry?b. The result of part (a) is the upper limit. However, as a practical matter, better error performance will be achieved at a lower data rate. Assume we choose a data rate
Study the works of Shannon and Nyquist on channel capacity. Each places an upper limit on the bit rate of a channel based on two different approaches. How are the two related?
Given the narrow (usable) audio bandwidth of a telephone transmission facility, a nominal SNR of 56 dB (400,000), and a certain level of distortiona. What is the theoretical maximum channel capacity (kbps) of traditional telephone lines?b. What can we say about the actual maximum channel capacity?
What is the thermal noise level of a channel with a bandwidth of 10 kHz carrying 1000 watts of power operating at 50°C?
A digital signaling system is required to operate at 9600 bps.a. If a signal element encodes a 4-bit word, what is the minimum required bandwidth of the channel?b. Repeat part (a) for the case of 8-bit words.
What is the channel capacity for a teleprinter channel with a 300-Hz bandwidth and a signal-to-noise ratio of 3 dB, where the noise is white thermal noise?
Given an amplifier with an effective noise temperature of 10,000 K and a 10-MHz bandwidth, what thermal noise level, in dBW, may we expect at its output?
a. Suppose that a digitized TV picture is to be transmitted from a source that uses a matrix of 480 * 500 picture elements (pixels), where each pixel can take on one of 32 intensity values. Assume that 30 pictures are sent per second. (This digital source is roughly equivalent to broadcast TV
IRA is a 7-bit code that allows 128 characters to be defined. In the 1970s, many newspapers received stories from the wire services in a 6-bit code called TTS. This code carried upper- and lower case characters as well as many special characters and formatting commands. The typical TTS character
Figure 3.5b shows the frequency domain function for a single square pulse. The single pulse could represent a digital 1 in a communication system. Note that an infinite number of higher frequencies of decreasing magnitudes is needed to represent the single pulse. What implication does that have for
Figure 3.4 shows the effect of eliminating higher-harmonic components of a square wave and retaining only a few lower harmonic components. What would the signal look like in the opposite case—that is, retaining all higher harmonics and eliminating a few lower harmonics?
Consider two periodic functions f1(t) and f2(t), with periods T1 and T2, respectively. Is it always the case that the function f(t) = f1(t) + f2(t) is periodic? If so, demonstrate this fact. If not, under what conditions is f(t) periodic?
Find the period of the function f(t) = (10 cos t)2.
Decompose the signal (1 + 0.1 cos 5t) cos 100t into a linear combination of sinusoidal functions, and find the amplitude, frequency, and phase of each component. Hint:Use the identity for cos a cos b.
If the solid curve in Figure 3.17 represents sin(2πt), what does the dotted curve represent?That is, the dotted curve can be written in the form A sin(2pft + f); what are A,f, and f?
Sound may be modeled as sinusoidal functions. Compare the relative frequency and wavelength of musical notes. Use 330 m/s as the speed of sound and the following frequencies for the musical scale. Note C E F G A B Frequency 264 297 330 352 396 440 495 528
Express the following in their simplest form:a. sin12pft - p2 + sin12pft + p2b. sin12pft2 + sin12pft - p2
A signal has a fundamental frequency of 1000 Hz. What is its period?
a. For multipoint configuration, only one device at a time can transmit. Why?b. There are two methods of enforcing the rule that only one device can transmit. In the centralized method, one station is in control and can either transmit or allow a specified other station to transmit. In the
What key factors affect channel capacity?
Define channel capacity.
What is the relationship between a signal’s spectrum and its bandwidth?
Define fundamental frequency.
What is the relationship between the wavelength and frequency of a sine wave?
How many radians are there in a complete circle of 360 degrees?
What are three important characteristics of a periodic signal?
Differentiate between an analog and a digital electromagnetic signal.
Use poll() function and socket programming to receive out-of-band data. Out-ofband data is also called urgent data in TCP, and is often received with first priority via a separate data stream. Hint: Check events and select POLLPRI.
Modify the server program from Exercise 2.4 to set the TCP window size for the server socket. Hint: Set the SO_RCVBUF size through a call to setsockopt(). Be aware that setting the TCP window size in this way would not guarantee the size for the entire life of the socket because of the inherent TCP
Write a stream-based echo server and a client sending messages to it, and receiving back each message in turn. Hint: Modify the stream-based TCP client and server programs in this chapter or similar programs to transfer multiple messages back and forth (until the client terminates the connection).
How to broadcast a message on the Internet? Two questions need to be answered:What address should be used as the broadcast address. How to send data to the broadcast address? A broadcast address is the subnet’s network number with all onebits set for the host portion of the address. For instance,
Write a sockets program to get a host name for a given IP address.
Determining a local machine’s IP address is useful when you are handling network communication tasks. Write code to find the IP address of a local machine. Hint: You may use some public DNS, for example, Google public DNS is 8.8.8.8.
This problem concerns material in Appendix E. Based on the principles enunciated in Table E.1.a. Design an architecture with eight layers and make a case for it.b. Design one with six layers and make a case for that.
We have seen that in order to deal with lost packets, TFTP implements a timeoutand-retransmit scheme, by setting a retransmission timer when it transmits a packet to the remote host. Most TFTP implementations set this timer to a fixed value of about 5 seconds. Discuss the advantages and the
In order to be able to retransmit lost packets, TFTP must keep a copy of the data it sends. How many packets of data must TFTP keep at a time to implement this retransmission mechanism?
The TFTP specification (RFC 1350) states that the transfer identifiers (TIDs) for a connection should be randomly chosen, so that the probability that the same number is chosen twice in immediate succession is very low. What would be the problem of using the same TIDs twice in immediate succession?
A user on a UNIX host wants to transfer a 4000-byte text file to a Microsoft Windows host. In order to do this, he transfers the file by means of TFTP, using the netascii transfer mode. Even though the transfer was reported as being performed successfully, the Windows host reports the resulting
What is the limiting factor in the time required to transfer a file using TFTP?
The previous version of the TFTP specification, RFC 783, included the following statement:All packets other than those used for termination are acknowledged individually unless a timeout occurs.The RFC 1350 specification revises this to say:All packets other than duplicate ACK’s and those used
Why does the TCP header have a header length field while the UDP header does not?
Why is UDP needed? Why can’t a user program directly access IP?
In Figure 2.5, exactly one protocol data unit (PDU) in layer N is encapsulated in a PDU at layer 1N - 12. It is also possible to break one N-level PDU into multiple 1N - 12-level PDUs (segmentation) or to group multiple N-level PDUs into one 1N - 12-level PDU (blocking).a. In the case of
A broadcast network is one in which a transmission from any one attached station is received by all other attached stations over a shared medium. Examples are a bustopology local area network, such as Ethernet, and a wireless radio network. Discuss the need or lack of need for a network layer (OSI
Two blue armies are each poised on opposite hills preparing to attack a single red army in the valley. The red army can defeat either of the blue armies separately but will fail to defeat both blue armies if they attack simultaneously. The blue armies communicate via an unreliable communications
List the major disadvantages with the layered approach to protocols.
a. The French and Chinese prime ministers need to come to an agreement by telephone, but neither speaks the other’s language. Further, neither has on hand a translator that can translate to the language of the other. However, both prime ministers have English translators on their staffs. Draw a
Using the layer models in Figure 2.15, describe the ordering and delivery of a pizza, indicating the interactions at each level.
Compare the address space between IPv4 and IPv6. How many bits are used in each?
Does all traffic running on the Internet use TCP?
Which version of IP is the most prevalent today?
What is a router?
What are some advantages to layering as seen in the TCP/IP architecture?
What is TCP/IP?
What is a protocol data unit (PDU)?
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