長期進化(LTE) is a mobile communications technology created to satisfy the requirements of applications focused on machine-to-machine (機對機) 或物聯網 (物聯網) 連接性.
1. LTE是什麼意思?
LTE was intended to be an improved version of 3G, but with further development, it has gone beyond the original goals of the creators. It was only planned to be 3.9G, but successive versions have become full 4G due to ongoing enhancements.
TD-LTE and LTE FDD are the two primary variations of LTE in terms of versions. The two systems are used in various ways depending on the 2G and 3G networks. 例如, China Mobile adopts TD-LTE because TE-LTE can function well with the 3G network that China Mobile independently constructed. Unicom and Telecom are free to utilize any of the two versions alone or a mix of the two.
2. What does LTE-M stand for?
A wireless interface called Lte-m facilitates the connectivity of 物聯網 and M2M devices with modest data transmission rate requirements. Let-m is a low-power wide-area (對不起) 科技. Compared to traditional cellular communications technologies like 2G, 3G, or higher LTE, the technology allows more extended battery life and broader in-building coverage. The key characteristics are:
- A full range of motion and in-car switching
- low energy use,
- more coverage within the structure
- supports VoLTE
Even when end devices are not directly linked to the grid, batteries that may last up to 10 years on a single charge can assist in lowering maintenance costs for deployed devices.
The interface may be utilized for applications that need some degree of human-computer interaction, such as specific health and safety applications like indwelling solutions and alarm panels, thanks to supporting VoLTE voice (4G+ HD voice) capabilities.
3. What is LTE CAT M
A low-power wide-area (對不起) 科技 called LTE Cat M, commonly referred to as LTE-M, 旨在利用蜂窩技術實現“大規模物聯網”, 或數千億 (!) 物聯網設備. 由於 CatM2 的採用還需要幾年時間, 術語“CatM”主要指 CatM1.
為了分離連接到 LTE 網路的每個設備的功能, LTE 無線電技術採用「類別」。稱為 CatM1 的設備系列使用受限的 1.4MHz 頻道來運行, 記錄的下載速率在 589Kbps 範圍內，上行速率為 1.1Mbps (3GPP版本 14). 與 Cat4 設備相比, 它可以採用載波聚合並提供高達 150Mbps 的下載速率, Cat1 裝置支援高達 10Mbps 的下載速度. 較低的速度 (300Kbps 下行/375Kbps 上行) 適用於較舊的 Cat-M 模組.
4. How LTE-M works
In version 13 of the 3GPP standard, which specifies the narrowband Internet of Things (NBIoT or LTE Cat NB1, both LPWA technologies in the licensed spectrum), lt-m was first presented as LTE Cat M1. The 3GPP’s 14th revision created the LTE Cat M2 standard. While LTE Cat M2 will expand to 5 兆赫茲, LTE Cat M1 delivers data at a bandwidth of 1.4 兆赫茲. The standard will result in advancements in the following areas:
Data transmission rate
LTE Cat M1 is perfect for many 物聯網應用 with low to medium data transfer rate needs since it can handle up to 375 KB/s uplink and downlink rates in half-duplex mode. The LTE Cat M2 will boost data throughput to a peak upload rate of 2.6 Mb/s and a peak download rate of 2.4 Mb/s, expanding the use of LTE-M even for applications requiring relatively high data transfer rates, such as video surveillance. Remote wireless firmware updates (FOTA) are also quicker, 更有效率, and need less battery charge at these rates. LWM2M (Lightweight M2M), a small and lightweight protocol for internet of things applications, is supported by U-Blox for FOTA updates.
Mobility
Compared to the mobile characteristics currently enabled by version 13 of LTE-M, 版本 14 of LTE-M now provides some benefits, including reduced power consumption and complete mobility (within and across frequencies) for mobile apps. Since it manages handovers between base stations like high-speed LTE, LTE-M is superior to NB-IoT for mobile use cases. An LTE-M device will function like a 細胞的 phone and never be disconnected, 例如, if a vehicle has to pass through many separate network units to go from point A to point B. 反而, after arriving at the new network unit, NB-IoT devices must eventually create a new connection.
5. LTE-M technologies: CAT-M1 and CAT-M2
Features of LTE CAT 1
- Latency is low (50 to 100ms)
- LTE medium-speed standard
- Suitable for IoT applications that need a lot of bandwidth
- Greater building penetration
- Full-duplex FDD/TDD and VoLTE support (LTE voice service)
- Meet appropriate data uplink and downlink speeds
- 物聯網 and M2M communications are supported.
- 3G and 2G are backward compatible.
- Increased data transfer efficiency
- Downlink (10Mb/s) and uplink (5Mb/s)
- Voice assistance
- 使用簡單
- Indoor protection
- Support for mobile devices
- Power consumption has been optimized in order to prolong battery life (up to 5 年)
- Low power standby and sleep modes are supported.
- Device for remote control
- Meager cost
NB-IoT/ CAT-M2
Although NB-IoT (also known as CAT-M2) performs a similar function to CAT-M, it employs DSSS modulation. Because NB-IoT cannot function in the LTE spectrum, operators must pay more upfront to adopt the technology.
通常, gateways in other infrastructures are used to collect sensor data and subsequently connect to the primary server. 然而, the primary server will get sensor data immediately, thanks to NB-IoT technology. 另外, NB-IoT is regarded as the less expensive solution since there is no need for gateways. 因此, Huawei, 愛立信, Qualcomm, and Vodafone are investing significantly in the NB-IoT commercial application. By the end of 2018, several worldwide areas are expected to have NB-IoT and LTE-M base stations deployed, according to Sierra Wireless.
6. Differences between LTE-M and NB-IoT
Performance Delay
Low energy usage and good dependability in tough environments are two benefits of NB-IoT technology. NB-IoT is less appropriate for applications that call for very low network latency than LTE-M is. While LTE-M latency is often 100 到 150 毫秒, NB-IoT 延遲通常等於或小於 10 秒 (關於 1.6 到 10 秒).
Device mobility
與 LTE-M 相比，NB-IoT 並不能完全實現行動性, 它還支援語音. 它是“完全無縫移動”的 LTE-M。 NB-IoT 仍然能夠用於行動資產和設備; 正如我們有時聽到的, 這只是有限的. 帶追蹤器的即時 NB-IoT 應用, 共享單車應用, 環境應用 具有移動組件但吞吐量低, 和智慧物流只是幾個例子. 固定資產, 例如智慧電錶或銷售點終端, 經常但不僅僅用於 NB-IoT.
Energy efficiency
與 LTE-M 相比, NB-IoT也更面向低能耗、低功耗，潛在電池壽命可達十年以上.
滲透
具有 NB-IoT, increased transmission power density is possible since it employs a single, 200KHz or 180KHz narrow band with smaller bandwidth. It elevates deep penetration capabilities (and increases overall coverage) over LTE-M and other improvements. For interior coverage, LTE-M also works, although NB-IoT is superior.
Technical details regarding coverage, reach, and depth of penetration: The maximum coupling loss for NB-IoT is 164 dB, which is a 20 dB improvement over GPRS‘s link budget.
7. What is the difference between LTE and LTE-M
The two issues at hand have two solutions recommended by 3GPP: LTE-u (LTE-unlicensed) and LTE-M (LTE-Machine to Machine).
The fundamental purpose of LTE-u is to address the present network speed, capacity, and user equipment on-demand contradictions. A carrier aggregation plan calls for spectrum, and because there isn’t enough approved spectrum to meet this need, the R13 proposes an authorized alternative: employing spectrum as the primary carrier. In order to accomplish the impact of carrier aggregation and increase rate and capacity, the unlicensed 5G spectrum is used as an auxiliary carrier.
Another alternative, primarily for the Internet of Things, is LTE-M, which was suggested in R12 and will be expanded upon in R13. 換句話說, the LTE spectrum is used to simplify the system and make it compatible with the Internet of Things’ low power consumption, high latency, and poor performance.
Only two alternatives are suggested to maintain 3GPP’s unwavering position in the wireless industry while adapting to the current new trend.
8. What is the coverage of LTE Networks
Factors that determine coverage
The signal in the LTE system may be split into uplink and downlink directions. The uplink coverage, or the coverage of the signal supplied by the terminal, determines the base station’s coverage due to the stark disparity in signal transmission strength.
How does the base station determine that it has received a signal from the terminal, then? The SINR, or signal-to-noise ratio, is used in this instance as the primary signal indication.
The most critical component in determining coverage is SINR
換句話說, the base station’s received terminal signal’s SINR satisfies the minimal standard. The terminal in this instance is on the coverage border, which corresponds to the coverage area’s maximum.
The factors that affect SINR
Only the base station or user is tall enough to overcome the earth’s curvature since the planet is spherical. The typical base station antenna hanging height is 30 米, with a coverage distance of roughly 20 公里. 然而, the calculation shows that if the base station or terminal height is 2 公里, the maximum coverage distance may be expanded to around 160 公里.
By the way, Ericsson has tested LTE using specialized terminals aboard flights. 然而, mounting the terminal atop a balloon at a distance of 2 km is also highly practical.
Another option is to construct a base station atop a 2-kilometer mountain, such as the summit of Huangshan Mountain, in order to cover a 160-kilometer region, nearly equivalent to Zhejiang Province.
The fact that there is only one base station and one user below it, with no interference I and just noise N, is the more crucial requirement. So even if you don’t utilize TA, the SINR doesn’t degrade.
There are several base stations and users beneath each base station in a typical network. The TA mechanism must be used to prevent interference from adjacent users, and its maximum processing capacity is 100 公里, which is where the term “100 kilometers” came from.
Expand the TA’s processing power
If you believe that TA is insufficient, you may also learn from the 全球行動通訊系統 processing approach to increase TA’s processing power.
9. What is the LTE bandwidth
LTE-M, an up-and-coming technology recently used in rail transportation, can only utilize a maximum bandwidth of 20M between 1785MHz and 1805MHz, and both the left and right frequency bands are already in use by other communication systems. 所以, omitting the frequency isolation band, the usable bandwidth, when utilized on the ground, is just 15M or 10M. It must also be shared with the oil, electrical, and transportation sectors. Physical barriers in separate tubes separate the upstream and downstream of the classic subway’s underground section. It is possible to employ a network of several cells operating at the same frequency, with the upstream and downstream occupying a maximum bandwidth of 20M each. Since the upper and lower lines share a 10M or 15M bandwidth and there is no physical separation between them, the cloud rail can only be covered by a single cell for a single hole and double track, similar to a subway therefore LTE-M can currently only handle CBTC and PIS systems. 然而, LTE-M has a cluster system of its own that can replace the TETRA system, which lowers the cost.
10. Introduction to LTE-M communication protocol
LTE Protocol Architecture
The user plane protocol stack and control plane protocol stack are two subsets of the E-UTRAN system’s air interface protocol stack. Physical layer (物理層), media access control (蘋果), Wireless Link Control (RLC), and packet data aggregation (PDCP) are the four layers that make up the user plane protocol stack. At the network side’s eNode B entity, these sublayers end.
The LTE system divides the data processing process into many protocol levels. Several protocol layer entities handle IP packets used for downlink data transmission before being delivered over the air interface. The entire protocol architecture for downlink transmission in LTE networks is shown in the above image.
Numerous methods are used in the actual design to represent the chip’s performance best. Coding and decoding, modulation and demodulation, multi-antenna mapping, and other telecommunications physical layer operations are all performed at the physical layer. The protocol’s most sophisticated layer is also the one that undergoes the most product testing. It must cooperate with hardware and is strongly tied to hardware.
- MAC層: manages upstream and downstream scheduling as well as HARQ retransmission. Retransmission and scheduling may be done properly, and the rate will be represented for the whole product, which is to say that the essence of L2 is there.
- NAS layer: handles information transfer between UE and MME. Information about users or controls may be included in the material. This includes user administration, security management, and session management. The AS layer, which we refer to as being behind the NAS layer, is transparent to eNode B. As observed in the accompanying image, eNode B lacks this layered protocol; therefore all NAS communications travel through to it.
- RLC layer: accountable for high-level data segmentation and connectivity, retransmission processing, and sequential transmission.
- RRC layer: eNode B’s most important signaling protocol, supporting various operations between terminals. It encompasses wireless resource algorithms, which in a broad sense govern wireless behavior in real-world applications.
- PDCP layer: is in charge of compressing headers to lower the quantity of bit traffic that the wireless interface must broadcast.
11. Introduction of LTE frequency
The standard organizations established by 3GPP, which are in charge of LTE and 5G, are LTE-m (Long-term Evolution of Machines) 和窄頻物聯網 (窄頻物聯網). They provide carriers the chance to use their current mobile infrastructure to facilitate the broad use of 物聯網設備. They are trustworthy and safe and can provide a dependable level of service as long as they stay within their mission.
Machine-to-machine (機對機) 溝通, sometimes referred to as MTC, includes both NB-IoT and MTC. They may assist with implementing programs like asset tracking, 環境監測, and smart cities. From the beginning, carriers have previously utilized 2G and 3G networks for specific IoT applications, such as fleet monitoring. LTE-M and NB-IoT can both transfer modest quantities of data over extended periods, 然而, they are not the same as IoT devices. They are thus less complicated and expensive than other mobile phone standards. Transformation: The device’s battery life may last up to 10 years because of its ultra-low power usage. These networks are frequently referred to as low-power WANs because of this (低功耗廣域網).
12. Advantages of LTE technology
- LTE communication technology has many advantages over earlier wireless communication technologies, including quick communication speeds, a broad network spectrum, flexible communication, powerful terminal functionality, high intelligence, good compatibility, more value-added communication services, high communication quality, and high-frequency band efficiency.
- High communication rate: The downlink peak rate of LTE is 100Mbit/s, and the uplink peak rate is 50MBit/s, which is several times faster than the 3G wireless communication system. LTE communication technology offers variable bandwidth, up to 20MHz.
- High spectral efficiency: Compared to 3G wireless communication systems, LTE communication technology significantly improves spectral efficiency via carrier aggregation, 正交頻分複用, 和其他技術. Uplink spectral efficiency can reach 2.5 bit/s, while downlink spectral efficiency can reach 5 bit/s (s.hz).
- LTE wireless communication system is based on packet switching in the overall architecture with high data rate, 低延遲, and packet domain service optimization as the primary goals.
- QoS guarantee: Distinct wireless communication applications have different QoS specifications. Through a rigid QoS mechanism, the LTE wireless communication system guarantees the quality of service for a variety of services, including real-time services (VoIP) and network surfing.
- 低延遲: Within the user plane, the unidirectional transmission latency is less than 5 ms. Less than 50ms pass between the control plane, migrating from the sleep state to the active state. During migration, less than 100ms pass between the dwell state and the active state.
- Good convergence: The next-generation network (NGN) 建築學, which LTE wireless communication system adopts, enables convergence and coexistence with 無線上網 and other wireless communication technologies, forming a multi-level wireless network environment. LTE wireless communication system also supports richer mobile services, such as multimedia information, 視訊通話, broadband data transmission, conference television, 和更多. Users may quickly get whatever information services they need.
- High degree of flexibility: LTE wireless communication system adopts all-IP network architecture, the system network architecture is flat, and the system networking and expansion flexibility are high. LTE communication technology supports paired or unpaired spectrum and can be flexibly configured with 1.25 MHz to 20 MHz bandwidth.
13. Where is LTE used? LTE Applications.
The main benefit of TE-M is security. A SIM chip, which may be integrated into a circuit board and prepared in a factory to set up keys and signatures, is necessary for a device linked to a phone. These embedded keys cannot be changed without having physical access to the device after they have been set up for the SIM card.
An authentication and NSasuiteBaES-256 encryption service is offered by the security module SIM.
LTE-M also benefits from maintaining connectivity even when there is a power loss. Since he is connected to a cellular network, he doesn’t need an access point (美聯社), which remains linked as long as the IoT device’s battery is functioning normally.
Because of this, cellular IoT connection is extensively employed in crucial areas, including fleet management, home and office security, 和 power grid.
