Question

below is a direct sequence code division multiple access

Q1 A LTE system employs orthogonal frequency division multiple30 access (OFDMA) transmission for downlink transmission, in which users are allocated a specific number of subcarriers for a predetermined amount of time, referred to as physical resource blocks (PRBs) in the LTE specifications. A PRB is defined as consisting of 12 consecutive subcarriers for one slot in duration. Given that the subcarrier spacing is 15 KHz, and transmission bandwidth over a 2.7GHz carrier is 20 MHz, and 6 OFDM symbols (plus cyclic prefix) form a slot of 0.5 ms. Assume that the channel s: power delay profile at 2.7 GHz is : exp(-tt), where b#5 Determine the RMS (root mean square) delay spread. a) Determine the coherence bandwidth. b) c) Determine the bandwidth of one PRB d) If the cyclic prefix takes one fourth of an OFDM symbol, determine3 the maximum guard period. Is it a flat fading or frequency selective fading on each subcarrier? e) ) A user is assigned one PRB. Does the user experience flat fading or frequency selective fading? 9) Suppose that a user is on the high speed train traveling at a speed 4 of 300 km per hour. Determine the Doppler spread and coherence time over which the time correlation of the signals is larger than 0.5 is the channel in g) regarded as slow fading or fast fading? Why? h)

Answer 1

Giden Bu= Afe sublarricr Spacg PRe Sulo Cavias SKH2

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PRS c) SubCo 12 Subosvic 12 ofonm tme I PRB OCCuipies

a) ems ddla d - 9(la21 tsamnitd poer Dday fath

bi L Nof pothg POoer f Gath in 5 path Total foac

sprend erege delay bTL マ ニ odoy path Ti (| SME t(t

ody sprcnd L-H - 0