1 introduction
With the rapid development and impetus of mobile internet, smartphones and internet-based tablet computers, a growing number of mobile communications users have evolved into mobile internet users, thus contributing to the explosive growth of mobile data flows. Td-lte is an innovative technology that has been developed to integrate the characteristics of the internet and mobile communications, and is a new time technology that is now widely emerging in china's communications sector. At present, with the country-wide commercialization of td-lte, the rapid maturity of the td-lte industrial chain, particularly the various tdd-type end products, will be further advanced, and td-lte will become an overall future development in the field of communications. In order to address the problems that may arise in the future in building a larger network of td-lte, this paper explores and analyses the methodology for planning and optimizing the network of td-lte。
2td-lte network concept
Td-lte, the timedivision-longtermevoltion (long-term evolution), is the fourth generation (4g) of mobile communication technology and standards developed jointly by operators such as alcatel, nokia siemens, da tang telecommunications, and hua for technology, chinese communications and chinese mobile. The design objectives of the td-lte technology are as follows: flexible bandwidth configuration to support 1. 4 mhz, 3 mhz, 5 mhz, 10 mhz, 15 mhz and 20 mhz; peak rate (20 mhz bandwidth) of 100 mbit/s down, up 50 mbit/s; control surfaces of less than 100 m and user faces of less than 5 m; access to 100 kbit/s for users with a speed greater than 350 km/h; support for enhanced mbms (e-mbms); elimination of cs domain, cs domain operations in the ps domain, e. G. Voip; simple system structure, low cost networking。
3td-lte key technology
3. 1 physical layer technology
The td-lte network physics layer technology includes basic transmission technology and multi-site technology, coding regulation technology, mimo technology and frame structure. The use of ofdm in the lte transmission technology mitigates the effects of time dispersion on the system resulting from the multi-routing extension of the wireless channel. In terms of channel codes, lte uses turbo codes and mmo techniques that can be adapted to various environments, such as macro, micro, hot spots. At the same time, the length of the 2 seed frames, i. E. The basic frame length of 0. 5 ms, is specified, and 0. 675 ms frame length is used when considering compatibility with the td-scdma system。
3. 2 network layer technology
Lte and its traditional 3gpp access network have reduced rnc nodes, introduced a single layer structure consisting of nodeb, facilitated the simplification of networks and reduced time lags, achieved low complexity, time delay and low cost requirements, and gradually moved closer to the typical ip broadband network structure。
4td-lte network planning
In the initial phase of the td-lte network, the main layout was in high-data flow areas, reducing the 2g network load and meeting user demand for high-speed data. The initial network layout, taking into account both coverage and capacity, combined with the current network 2g/3g data flow site distribution, and with the full utilization of the existing 2g/3g network site resources and associated resources, will be appropriately in the form of new sites in some regions. Wireless planning for td-lte will be carried out in a continuous segment, targeting the various wireless network indicators in the signal coverage area to meet commercial requirements。
4. 1 needs analysis
Before planning td-lte, needs analysis, including the identification of overall networking strategies, networking indicators and the need to meet the specific needs of current users as well as development needs over a certain period of time. The data that need to be collected, such as existing web-based gsm/td-scdma base station information, business needs information, three-dimensional electronic maps, etc., will ensure the correct development of the subsequent td-lte wireless network planning only in advance of their high accuracy。
4. 2 network size estimates
The objective of the network size estimates is to establish a relatively specific base size for the construction of the td-lte network, a step that is largely determined by the two dimensions of the coverage and capacity estimates. This is done by estimating the number of base stations that meet established coverage requirements by determining the radius of area coverage and future coverage of the td-lte network in different regions, based on local wireless network dissemination models and the distribution of existing base stations. The volume estimate is an analysis and estimation of the capacity of the system that can be carried by the td-lte network, based on an analysis of time horizons and configuration conditions. An estimate of the size of the network results in a clearer programme and data for the successful implementation of the follow-up planning tasks。
4. 3 site planning
The third stage of the planning of the td-lte network is the site planning phase, which involves the completion of the initial layout of the network site in conjunction with the site resources of the current network and the proposed new site in the budget for the network link. Once the initial layout has been completed, the availability of sites will need to be further revised in conjunction with existing information or site surveys to determine the availability of sites, leading to the finalization of existing sites and the creation of new sites covering the area. The planning process should take into account such factors as the geographical wireless environment around the site and the conditions for the operationalization of the project。
4. 4 network simulation
The network simulation phase requires detailed parameters and simulation tests, including testing of the planning programme using the corresponding td-lte simulation tool, with emphasis on coverage and capacity simulation. Specifically, it should include planning data imports, dissemination forecasts, neighbourhood planning, time horizon and frequency planning, user and business model configurations and monte carlo simulations. The results should be carefully considered for compliance, with a focus on data close to the critical mass to ensure that the network is operational as expected. In addition, it includes the setting of detailed parameters, including basic parameters for sub-regions such as antenna height, direction angle, lower inclination, neighbourhood planning parameters, frequency planning parameters, pci parameters, etc。
4. 5 wireless parameter planning
Planning for the configuration of the td-lte wireless network parameters includes neighbourhood planning, frequency planning and disturbance code (pci) planning。
(1) neighbourhood planning
Td-lte neighbourhood planning is carried out on the basis of an integrated consideration of sub-district attributes, coverage, station spacing, azimuth, etc., and is broadly the same as that of the 3g network. While rational neighbourhood planning is carried out with the network, particular attention needs to be paid to neighbourhood planning with different systems, such as td-scdma and gsm, so as to avoid coverage anomalies arising from the unreasonable location of the neighbourhood。
(2) frequency planning
There are currently two groups of the same frequency and the same frequency. In the same frequency network, all sub-regions can use the same frequency, with a high frequency utilization rate, with strict requirements for regularity between sub-channels, avoiding frequency interference mainly by means of randomization of interference, elimination of interference and coordination of interference. In the iso-frequency network, the adjacent sub-regions use different frequencies in order to reduce interference, are less efficient than the same frequency in the spectrum, and, because rrm algorithms are simple, have a higher marginality rate than the same-frequency network. The network is limited to frequency band resources, has a balance between jamming controls and frequency band use and requires reasonable frequency planning to ensure minimal network interference。
(3) pci planning
Lte's physical area identification pci is used to facilitate the separation of wireless signals from different sub-areas by terminals. The pci covers the only area in any district, and the adjacent area of a district cannot have the same pci. Based on the objective of achieving simplicity, clarity and ease of expansion, the planning principle currently used is that the pci at the same site is assigned to the same pci group and the pci at the adjacent site is assigned to the different pci groups. In the case of indoor coverage, planning needs to take into account the need for separate planning。
5td-lte network foundation optimization
5. 1 td-lte network optimization definition
The optimization of the td-lte wireless network is mainly to maximize user awareness by adjusting the various wireless system parameters and the wireless network engineering design parameters to meet the requirements of the various wireless network indicators in the various existing operations. Since the system's requirements for wireless networks are constantly changing, optimizing the adjustment process is often a cyclical process. Depending on the stage at which the network is built, the td-lte network optimization is generally divided into the engineering and transport optimization phases. Project optimization, i. E. Network optimization, includes, inter alia, single station validation, cluster optimization, county and city optimization, and network optimization, which refers to day-to-day optimization, which is the optimization of the network during the course of the network's work, primarily the analysis of data collection for the operational network and the identification of the reasons that affect the quality of the network in order to optimize its functioning. The td-lte network has three main goals: optimal system coverage, reasonable switch belt control, and minimal system interference。
5. 2 td-lte network foundation optimization method
The td-lte network's optimization methods include, inter alia, gift optimization, power adjustment, neighbourhood optimization, small area pci optimization, re-selection, switching parameters optimization, feature algorithm application, etc. These approaches are mutually reinforcing and indispensable。
5. 2. 1 day feed optimization
Astronomical optimization is the focus of the td-lte base optimization, which changes the intensity of the jamming signals in the area, mainly by adjusting the directional angles of the antenna and the lower angles of the antenna in the field, on the basis of the principle of increasing the electrical level of the main covered sector and reducing the level of electricity in other sectors, thereby altering the distribution of signals in the region and eliminating the phenomena of unreasonable coverage, weak coverage, cross-section coverage and frequent switching。
5. 2. 2 power adjustment
Power adjustments can be used in conjunction with antenna adjustments to meet the requirements of small area coverage, the switch is in line with expectations and the quality of signals is enhanced。
5. 2. 3 neighbourhood optimization
The optimization of the neighbourhood makes it possible to re-select and switch between stations. (b) an analysis of the network-wide neighbourhood relationship and the adaptation of the neighbourhood's missing and redundant areas to optimize the neighbourhood relationship and upgrade network indicators such as the transition success rate。
5. 2. 4 subsector pci optimization
Inadequate pci planning between neighbourhoods can lead to an increase in interference between neighbourhoods, affect user perceptions and improve the overall quality of the network through optimization of pci between neighbourhoods。
5. 2. 5 re-selection, switching parameters optimization
The user's idle-state process is optimized by adjusting the re-selecting parameters, ensuring that the user re-selects and calls, and increasing the success rate of access; adjusting the switching parameters to ensure continuity and user perception of the user's business。
5. 2. 6 feature algorithm application
Upon completion of the optimization of the network base, the overall performance of the network can be enhanced through feature algorithms, such as access control, load control, interference-resistant icic algorithms, and bf algorithms that reduce interference and increase user throughput。
6 concluding remarks
The scientific and well-planned design of the td-lte wireless network is of great importance for the future deployment of the network. This paper examines the planning of the td-lte wireless network in five stages, namely, needs analysis, network size estimation, site planning, simulation of the network, wireless parameter planning, and presents the underlying optimization methods of the td-lte network. However, as td-lte is an emerging technology that needs to be continuously developed and refined in practical applications, the planning and optimization of td-lte also needs to be continuously improved and upgraded。
Submitted by: zheng guo hui unit: china mobile communications group, zhejiang ltd
