the purpose is to improve the rate, will mention radio frequency signal, can transmit information quickly, but the higher the performance of the modulation, need the signal quality of the higher, which is closely linked with the wireless environment, among them, the adaptive modulation coding (AMC) is based on the information feedback of channel quality choose the most appropriate way of modulation, to adjust the size of the amount of data and data rate, for a good channel, reduces redundant coding, for channel with poor quality, increase the redundancy coding is required to reduce interference;
By far the most popular antenna technology is the , multiplexing and diversity it is two kinds of working mode, reuse refers to the different antenna to send data, can increase the capacity and diversity pattern is multiple antennas to send the same data, under the condition of weak environment can improve the rate of users;
when more bandwidth is needed to use, it USES the FFT technology, through the design within a bandwidth, multiple orthogonal sub-carrier can obviously increase the spectrum utilization, and the ability to combat frequency selective fading, but it is sensitive to frequency offset and peaks are higher than;
users send rate refers to the base station regulation, some algorithms for scheduling algorithm with polling, and the maximum load dry than algorithm, proportional fair algorithm, etc.
neighborhood interference coordination it is worth noting that the center is to use a pair of frequency, and the edge is the use of frequency, the method of interference coordination between have lower adjacent regions interference, improve cell edge user data throughput, edge to improve user experience, such as low interference at the expense of capacity at the expense of, traditional ICIC and dynamic and static, adaptive ICIC is ICIC by MR measurement judge channel environment, only in high load situations it is necessary to open the ICIC,
is a self-organization network more intelligent, more automation network, it includes base station from the start, neighbourhood relations (ANR) automatically, automatic switching optimization (MRO), minimize the road test (MDT) and so on several aspects,
About LTE frame structure, its overall long 10 ms, contains 20 time slot, each time slot length 0.5 ms, the adjacent two time slot and a frame, as scheduling cycle of LTE, td-scdma LTE contains three specific subframe (downlink pilot time slot (DwPTS), uplink pilot time slot (UpPTS), protection period (GP)) and muck frame configuration is 1:3, and the special child frame time slot allocation for 10:2:2, for 9:3:2 L band, a time slot inside and 6-7 symbol, the resources of the LTE unit is the resource block (RB), its bandwidth is 12 KHZ, every 12 sub carrier form a RB, another smaller particles (RE) resources, mainly in order to solve some use RB is too big, and that when
The td-scdma LTE technology principle of protocol stack has three layers, the user through a user to transfer business data, RRC signaling transmission via control surfaces,
physical broadcasting channel is a downlink channel, mainly used for loading master information block (MIB), the information contains the bandwidth, the frame number, PHICH configuration of the three more important information, each frame has a PBCH, on time slot 1 in the first four symbols, but its scheduling cycle is 40 ms, behind three PBCH on the frame and the first frame is the same,
random access process is the user send random access to the base station (by PRACH channel), base stations distributed random access response (through) PDSCH channel, after the user to send high-level information to the base station (by PUSCH channel), random access sequence including leading (plot sequence), leading the signature, protect time interval (ensure that users in the corresponding configuration base stations within the time window leading sequence and submit it to the base station), PRACH there are five kinds of formats, including length of time window for special child frame for TDD is special, generally 0 format is enough, it is about 15 km, the radius of the coverage area
neighborhood search process for PLMN selection request - & gt; Neighborhood search - & gt; System message to accept - & gt; Selection and reside community - & gt; PLMN selection response - & gt; Random access - & gt; To attach, neighborhood search phone turned on PSS monitoring (to observe whether the time slot synchronization and access to the physical id) and SSS monitor (monitoring frame synchronization and cell IP, FDD/TDD, CP),
RRC including to control the surface connection is established, the public processes and user surface connection is established, the RRC set up is completed, the base station to activate the NAS, the user can transfer initial message to MME,
LTE network architecture and interface for us to understand other knowledge plays a very important role, its schematic diagram is as follows,
In LTE networks have a track area (TA), the concept of it is in order to confirm the location of the mobile station, with TAC TA codes to identify, a TA may contain one or more of the village,
Multiple TA is TA List,
TAI=MCC + + TAC newsun focus it is the only identity, a total of 6 bytes, the user will TA List in the Attach or TAU notifies the user, the user to save it,
TAU trigger
the condition ofEnter the new TA List; Update timer timeout cycle track area; Users from other district re-election to the E - UTRAN village,
LTE of indoor coverage design is an important technology, because the 3 g era indoor business accounts for 70%, 70% of complaints in indoor, covering the target selection and analysis of preliminary site investigation, covering estimate (capacity estimation), system detailed design, system installation, testing and optimization of multiple parts, among them, the indoor antenna cloth principle is to follow the "small power, antenna", in the process used to power splitters, combiner, coupler, attenuator, trunk amplifier, load and leakage cable,
RF optimization is mainly RF optimization (design to cover, switch, interference), and its concrete process for optimization (determine the optimization goal, road test, dividing Cluster, determine the test route, tools and materials to prepare), optimization of data collection, problem analysis, adjustment, appear weak coverage, covered more area, has not balance when they need to be optimized,
pilot pollution problem is to meet community number greater than 3 or RSRP (first) - RSRP (4) & lt;=6 db, it causes the area coverage, coverage surrounding environment influence, the azimuth Angle is unreasonable, village layout is unreasonable,
single site validation refers to a single site equipment function and coverage for the purpose of monitoring and validation, including preparation stage (tool set, test route planning), the test and analysis, if there is a problem, depending on the problem of the SSV records to adjust the proposal, if adjustment suggestion bai approved, will adjust, again to test, so, until finally SSV report is verified,
switching algorithm is more complex and important, it includes the frequency switching and pilot frequency switching two kinds, including the frequency switch by A3 event trigger, the incident report way around the cycle, the frequency switching, including user measurement switch base stations, base station switch command three steps, the pilot frequency switch directly to skip the pilot frequency measurement, direct switch, so in general, not to choose different frequency switching, because there is no measured cannot be determined after switch signal quality is better than before switching, different frequency switch is divided into necessary scenes and non-essential scene switching, such as the former is based on coverage, based on the quality of uplink, based on the distance, the latter such as based on the business, based on the load, based on the frequency of priority, based on the speed, plastic, based on carrier pilot frequency trigger if is based on the cover, then it is triggered by A3/A4, A5, and report the way around the cycle, based on others is triggered by an event A4,
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