Mobile exam questions

1. In the GSM network, an S2/2/2 base station can accommodate up to 42 wireless users’ calls at the same time. 2. Mobile communication systems currently use three multiple access methods: _FDMA_, _TDMA_ and _CDMA_. GSM uses FDMA/TDMA (or TDMA) multiple access methods. 3. The GSM system is divided into three parts according to functions: MSS, BSS and MS. 4. CCCH on the wireless interface includes three types of channels: PCH, AGCH, and RACH. 5. Common base station networking methods include star, chain, tree and ring flexible networking. 6. In the GSM system, the digital voice signal rate transmitted between the mobile station (MS) and the base station (BTS) is 13 Kbit/s, and the digital voice signal rate transmitted between the mobile switching center (MSC) and the base station is 64 Kbit/s. , so code conversion equipment needs to be added between BSS and MSC. 7. Diversity technology is an effective method to deal with fast fading. Among many diversity technologies, the most commonly used one in urban areas is __space diversity__. The most commonly used in suburban areas is polarization diversity. 8. Handover generally refers to the behavior that the MS performs due to location changes in the call state (idle, call). 9. In the GSM network, a 2M network can carry a maximum of 15 carrier frequencies. 10. The services that digital cellular PLMN can provide are divided into basic services and supplementary services. 2. True or False Questions: 1. If the phone does not have a SIM card, it cannot make any calls. (Error) 2. The HLR stores data such as mobile subscriber identification numbers, access capabilities, user categories and supplementary services. (Correct) 3. When the MSC pages the called user, it must send the paging command within the entire VLR range. (Error) 4. When a mobile user initiates a location update, a new TMSI is not allocated by the VLR every time. (Correct) 5. The GSM900/GSM1800 dual-band system can use the switching subsystem and base station controller, and can also connect to the base station. (Correct) 6. The GSM network personal authentication key Kc is stored only in HLR/AUC. (Error) 7. When TCH and SACCH are combined, 51 frames form a multiframe, and when the control channel is combined, 26 frames form a multiframe. (Error) 8. When the coverage radius of GSM cell is designed, even if the power output is adjusted to the maximum and the terrain is flat, the coverage range cannot exceed 35 kilometers.

(Correct) 9. During shutdown registration, the mobile phone can only be shut down after receiving a system confirmation message (Correct) 10. In the idle state, soft handover may be performed (Correct) 11. The standing wave ratio of the antenna feeder system must be greater than 1.4. (Correct ) 3. Multiple choice questions: 1. Which of the following channel types belong to the control channel A, C, D A, AGCH B, TCH/F C, FCCH D, SACCH2? How many wireless users can an S2/2/2 base station accommodate at the same time? call? B A, 36 B, 42 C, 48 D, 643. The possible reasons for the deterioration of the standing wave ratio of the antenna feeder system are: A, B, C, D A. The joints are not connected properly B The joints are not properly sealed resulting in water ingress C. Weather The standing wave of the feeder arrester is large D. There is damage somewhere in the feeder 5. Which of the following measures are used by the GSM system to improve spectrum efficiency (1, 2, 4) 1) Frequency hopping 2) DTX 3) Channel coding 4) Power control 6 , the following two-way channels are (1) 1) SACCH 2) AGCH 3) BCCH 7. The uplink measurement report is transmitted on (3): 1) SDCCH 2) RACH 3) SACCH 4) FACCH8, Siemens The reason why MSC can be interconnected with MOTOROLA's BSC is because there are standard (1) interfaces: 1) A 2) B 3) C 4) D9. What are the different possible reasons for call drop and handover failure: abcdA interference The degree is relatively high B Hardware failure C Antenna feeder connection direction is wrong D Cross-zone 10. In most cases, handover HOTRAFFIC based on cell congestion is: bA Mobile phone users in the center of the service cell switch to other cells to alleviate congestion; B. Switch mobile phone users at the edge of the serving cell to other cells to alleviate congestion; C. Switch new users who request channel occupation in the serving cell to other cells to alleviate congestion.

11. Ideas for handling handover failure: abcdA Check interference sources B. Eliminate possible hardware failures C. Reduce cross-coverage areas between cells D. Eliminate design deficiencies (there are same-frequency and same-BISC/same-frequency cells that are neighboring cells) Cellular Handover failure handling: eA Adjust the frequency and BSIC design B Adjust the definition of neighboring cells C Find problems with the indoor distribution system D Adjust the handover threshold E All of the above are possible 11. When the MS reselects the target cell, the information that does not need to be checked is ： dA cro B Cell bar C Location Area D Time advance12. Speeding up the handover speed can: bcdA handover success rate will decrease, B appropriately reduce call drops, C handover volume will increase, D BSC load will increase 13. Reasons for call drops: abcA High degree of interference B Hardware failure C Antenna feeder connection direction is wrong 14. Ideas for handling dropped calls: abcdA Check interference sources B Eliminate possible hardware faults C Reduce or increase the cross coverage area between cells D Check antenna connections 15. Improper setting of the LAC area causes too many location updates. What may happen to the mobile phone: dA The mobile phone has signal, but the called recording prompt is not in the service area B. The mobile phone has signal, but cannot be called C The mobile phone signal is unstable D All of the above are 16 The signal in the cell is very strong but the user cannot initiate a call (can switch to enter). Reasons: dA There is strong external interference B The cell is not defined in the exchange C The mobile phone mode does not match the GSM protocol (for example, some mobile phones that have not been upgraded are opening DCS1800 Area) D cell has no SDCCH channel defined. 20. Which logical channel is used in location update: bA, TCH B, SDCCH C, SACCH D, FACCH21. The methods to solve too many location updates are: abdA, re-plan location area B, and try to avoid cell duplication at the location area boundary. Select the frequent area C, configure multiple signaling channels D for the border cells, and modify the CellReselectHysteresis parameter 22. The GSM network uses the 900/1800MHz frequency band, where the mobile station transmits and the base station receives: BA 908-914MHz B 909-915MHz C 910 -916MHz 25. When mobile users use packet data services, they need to be assigned IP addresses. Equipment related to the core network packet part should also be assigned IP addresses, such as: A CA BSC, PCF B PDSN, RADIUS server and HLR C DNS server, firewall and various application servers 27. Calling number delivery principle in GSM/CDMA network In the regulations, the correct ones are: A. During the connection process of the call channel within the CA network, in principle, the calling number is not changed. B. When a GSM/CDMA user makes a calling, the calling number format in the network adopts an internationally valid number. C. Other domestic networks The calling number becomes a standard format when accessing China Unicom's GMSC and is transmitted within the network. 28. The following statements are incorrect: ABCA, the authentication process must occur before each call or location update. B. The Ciphering process must occur before each call or location update. C. The TMSI reassignment process must occur before each call or location update. D. The authentication process, Ciphering process, and TMSI redistribution process can be defined in the exchange so that they do not occur every time. 30. When the mobile phone is on a call, it switches to a cell in a new location area, then: C A, it will update the location during the call. B, it will update the location the next time it crosses the LAC area. C, it will update the location immediately after the call ends.

31. After the mobile phone is shut down normally, the following situations are correct: C A. The system will still send a PAGING request to it through the PAGING channel, although the mobile phone can no longer receive it. B. The short message is queued into the database. If it has not been updated before the user turns on the phone, the short message cannot be sent to the user. C. Call requests from other users to the mobile phone will be rejected. D. The short message sent to it will definitely be lost. 32. The following descriptions are correct: D A, each location update needs to involve HLR. B. Location updates all occur on different VLRs. C. The priorities of several types of location updates are the same. D. The storage location or guidance location of user data must be changed in each location update. 33. Which of the following technologies is not resistant to multipath fading: b a) Channel coding b) DTX c) Frequency hopping d) Interleaving 34. The main purpose of TMSI redistribution is: A A, anti-theft B, encryption C, roaming D, Supplement when the number of IMSI is insufficient. 35. Methods to solve excessive location updates include: ABD A, re-plan the location area B, try to avoid locations with frequent cell reselection at the location area boundary C, configure more signaling channels D for the cells at the boundary, and modify the CellReselectHysteresis parameter 4. Questions and Answers 1. Please list several reasons for handover failure (please list at least three) (1) Hardware problems (for example, there is a problem with the clock board and cannot be synchronized) (2) There is interference in the original cell and the HANDOVER cannot be decoded. COMMAND information; there is interference in the target cell (3) Island effect (same as BCCH, BSIC) (4) Shortage of channel resources in the target cell to be switched to (5) Poor wireless conditions prevent the MS from receiving the handover command from the original cell or being unable to occupy it The channel assigned by the target cell (poor wireless conditions are often caused by less coverage overlap between cells) (6) Coverage problem: There is not enough overlap between the target cell and the source cell (7) Due to the antenna being blocked or the same cell Uneven coverage of the two antennas leads to (8) The repeater amplifies the noise (9) Parameter setting problems: If the T3103 setting is too small, the MS does not have time to occupy the channel of the target cell (10) The A interface is overloaded and causes congestion. , resulting in no time slot available when transmitting handover requests and handover commands within the MSC or between MSCs. MSC's LAC table is not fully defined.

2. When the mobile station is in idle mode, the signal levels received by the mobile station from cell 1 and cell 2 are as follows: AV_RXLEV = 26 in cell 1, AV_RXLEV = 20 in cell 2

The specific parameters are as follows: cell 1 :

TXPWR_MAX_CCH = 39 dBm RXLEV_ACCESS_MIN = 20 CELL_RESELECT_HYSTERESIS = 4dB

Cell 2:

TXPWR_MAX_CCH = 33 dBm RXLEV_ACCESS_MIN = 14

MS Should cell selection be performed? a) If it is phase 1 MS, cell 1 and cell 2 belong to the same location area. b) If it is phase 1 MS, cell 1 and cell 2 do not belong to the same location area. Provide the following information: C1 = AV_RXLEV - ACCESS_MIN - Max (0, MS_TXPWR_MAX_CCH - P)MS GSM900 Phase 1, power class 3 = 37 dBm. CELL 1: C1=26-20-2=4CELL 2:: C1=20-14=6C1(CELL2)>C1( CELL1) Perform cell reselection with different LAC: When C1(CELL2)>C1(CELL1)+ CELL_RESELECT_HYSTERESIS, cell reselection will be performed. 3. If a BS240 base station is found to be down, but the power supply is good, the base station will be found after turning it on and off again. It still doesn't work properly, and trying to connect to the LMT failed (assuming the LMT is good). Please analyze what may be the general cause of such a failure, and what measures to take to recover. The COBA should be responsible for the connection function of the LMT. The COBA may be damaged or the backup board may be damaged, and the COBA needs to be replaced for recovery; 4. The BS240 base station is configured as 8/8/8, and the hardware includes a basic rack and two expansion racks. During the commissioning process, it was found that the creation of the three rack CU modules went smoothly, but when creating the DUAMCO for the extended rack, it was always unsuccessful. No matter how many times I try, the system prompts that the status of DUAMCO is "not installed". It is assumed that there is no problem with the backup board of the rack, and there is no problem with the cables connecting the racks. Please explain possible reasons. ACT fault, combiner damage, CAN BUS fault, COBA or COSA hidden fault, combiner backplane fault, COBA and COSA backplane fault, whether the internal wiring of the cabinet is tight. In fact, there are many online.