Problems in Software Maker Code 39 Full ASCII in Software Problems

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14 Problems using software topaint barcode code39 in web,windows application Ames Code 1. Consider an FD Software Code 39 MA system for multimedia data users. The modulation format requires 10 MHz of spectrum, and guard bands of 1 MHz are required on each side of the allocated spectrum to minimize out-of-band interference.

What total bandwidth is required to support 100 simultaneous users in this system 2. GSM systems have 25 MHz of bandwidth allocated to their uplink and downlink, divided into 125 TDMA channels, with 8 user timeslots per channel. A GSM frame consists of the 8 timeslots, preceeded by a set of preamble bits and followed by a set of trail bits.

Each timeslot consists of 3 start bits at the beginning, followed by a burst of 58 data bits, then 26 equalizer training bits, another burst of 58 data bits, 3 stop bits, and a guard time corresponding to 8.25 data bits. The transmission rate is 270.

833 Kbps. (a) Sketch the structure of a GSM frame and a timeslot within the frame. (b) Find the fraction of data bits within a timeslot, and the information data rate for each user.

(c) Find the duration of a frame and the latency between timeslots assigned to a given user in a frame, neglecting the duration of the preamble and trail bits. (d) What is the maximum delay spread in the channel such that the guard band and stop bits prevent overlap between timeslots. 3.

Consider a DS CDMA system occupying 10 MHz of spectrum. Assume an interference-limited system with a spreading gain of G = 100 and code cross correlation of 1/G. (a) For the MAC, nd a formula for the SIR of the received signal as a function of G and the number of users K.

Assume that all users transmit at the same power and there is perfect power control, so all users have the same received power. (b) Based on your SIR formula in part (a), nd the maximum number of users K that can be supported in the system, assuming BPSK modulation with a target BER of 10 3 . In your BER calculation you can treat interference as AWGN.

How does this compare with the maximum number of users K that an FDMA system with the same total bandwidth and information signal bandwidth could support (c) Modify your SIR formula in part (a) to include the effect of voice activity, de ned as the percentage of time that users are talking, so interference is multiplied by this percentage. Also nd the voice activity factor such that the CDMA system accommodates the same number of users as an FDMA system. Is this a reasonable value for voice activity 4.

Consider a FH CDMA system that uses FSK modulation and the same spreading and information bandwidth as the DS CDMA system in the previous problem. Thus, there are G = 100 frequency slots in the system, each of bandwidth 100 KHz. The hopping codes are random and uniformly distributed, so the probability that a given user occupies a given frequency slot on any hop is .

01. As in the previous problem, noise is essentially negligible, so the probability of error on a particular hop if only one user occupies that hop is zero. Also assume perfect power control, so the received power from all users is the same.

(a) Find an expression for the probability of bit error when m users occupy the same frequency slot. (b) Assume there is a total of K users in the system at any time. What is the probability that on any hop m there is more than one user occupying the same frequency (c) Find an expression for the average probability of bit error as a function of K, the total number of users in the system.

467. 5. Compute the ma ximum throughput T for a pure ALOHA and a slotted ALOHA random access system, along with the load L that achieves the maximum in each case. 6.

Consider a pure ALOHA system with a transmission rate of R = 10 Mbps. Compute the load L and throughput T for the system assuming 1000 bit packets and a Poisson arrival rate of = 10 3 packets/sec. Also compute the effective data rate (rate of bits successfully received).

What other value of load L results in the exact same throughput 7. Consider a 3-user uplink channel with channel power gains g 1 = 1, g2 = 3, and g3 = 5 from user k to the receiver, k = 1, 2, 3. Assume all three users require a 10 dB SINR.

The receiver noise is n = 1. (a) Con rm that the vector equation (I F )P u given by (14.6) is equivalent to the SINR constraints of each user.

(b) Determine if a feasible power vector exists for this system such that all users meet the required SINR constraints and, if so, nd the optimal power vector P such that the desired SINRs are achieved with minimum transmit power. 8. Find the two-user broadcast channel capacity region under superposition coding for transmit power P = 10 mW, B = 100 KHz, and N0 = 10 9 .

9. Show that the sum-rate capacity of the AWGN BC is achieved by sending all power to the user with the highest channel gain. 10.

Derive a formula for the optimal power allocation on a fading broadcast channel to maximize sum-rate. 11. Find the sum-rate capacity of a two-user fading BC where the fading on each user s channel is independent.

Assume each user has a received power of 10 mW and an effective noise power of 1 mW with probability .5 and 5 mW with probability .5.

12. Find the sum-rate capacity for a two-user broadcast fading channel where each user experiences Rayleigh fading. Assume an average received power of P = 10 mW for each user and bandwidth, B = 100 KHz, and N0 = 10 9 W/Hz.

13. Consider the set of achievable rates for a broadcast fading channel under frequency-division. Given any rate vector in CF D (P, B) for a given power policy (P and bandwidth allocation policy B, as de ned in (14.

30), nd the timeslot and power allocation policy that achieves the same rate vector. 14. Consider a time-varying broadcast channel with total bandwidth B = 100KHz.

The effective noise for user 1 has pdf n1 = 10 5 W/Hz with probability 3/4, and the value n 1 = 2 10 5 W/Hz with probability 1/4. The effective noise for user 2 takes the value n 2 = 10 5 W/Hz with probability 1/2, and the value n2 = 2 10 5 W/Hz with probability 1/2. These noise densities are independent of each other over all time.

The total transmit power is is P = 10 W. (a) What is the set of all possible joint noise densities and their corresponding probabilities (b) Obtain the optimal power allocation between the two users and the corresponding time-varying capacity rate region using time-division. Assume user k is allocated a xed timeslot k for all time where 1 + 2 = 1 and a xed average power P over all time, but that each user may change its power within its own timeslot, subject to the average constraint P .

Find a rate point that exceeds this region assuming you don t divide power equally.. (c) Assume now x Code 39 Full ASCII for None ed frequency division, where the bandwidth assigned to each user is xed and is evenly divided between the two users: B 1 = B2 = B/2. Assume also that you allocate half the power to each user within his respective bandwidth (P 1 = P2 = P/2), and you can vary the power over time, subject only to the average power constraint P/2. What is the best rate point that can be achieved Find a rate point that exceeds this region assuming that you don t share power and/or bandwidth equally.

(d) Is the rate point (R1 = 100, 000, R2 = 100, 000) in the zero-outage capacity region of this channel 15. Show that the K-user AWGN MAC capacity region is not affected if the kth user s channel power gain g k is scaled by if the kth user s transmit power P k is also scaled by 1/ . 16.

Consider a multiple access channel being shared by two users. The total system bandwidth is B = 100KHz. Transmit power of user 1 is P1 = 3mW, while transmit power of user 2 is P 2 = 1mW.

The receiver noise density is .001 W/Hz. You can neglect any path loss, fading, or shadowing effects.

(a) Suppose user 1 requires a data rate of 300 Kbps to see videos. What is the maximum rate that can be assigned to user 2 under time-division How about under superposition coding with successive interference cancellation (b) Compute the rate pair (R1 , R2 ) where the frequency-division rate region intersects the region achieved by code-division with successive interference cancellation (G = 1). (c) Compute the rate pair (R1 , R2 ) such that R1 = R2 (i.

e. where the two users get the same rate) for time division and for spread spectrum code division with and without successive interference cancellation for a spreading gain G = 10. Note: To obtain this region for G > 1 you must use the same reasoning on the MAC as was used to obtain the BC capacity region with G > 1.

17. Show that the sum-rate capacity of the AWGN MAC is achieved by having all users transmit at full power. 18.

Derive the optimal power adaptation for a two-user fading MAC that achieves the sum-rate point. 19. Find the sum-rate capacity of a two-user fading MAC where the fading on each user s channel is independent.

Assume each user has a received power of 10 mW and an effective noise power of 1 mW with probability .5 and 5 mW with probability .5.

20. Consider a 3-user fading downlink with bandwidth 100 KHz. Suppose that the three users all have the same fading statistics, so that their received SNR when they are allocated the full power and bandwidth are 5 dB with probability 1/3, 10 dB with probability 1/3, and 20 dB with probability 1/3.

Assume a discrete time system with fading i.i.d.

at each time slot. (a) Find the maximum throughput of this system if at each time instant the full power and bandwidth are allocated to the user with the best channel. (b) Simulate the throughput obtained using the proportional fair scheduling algorithm for a window size of 1, 5, and 10.

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