Mr. Wu is here mainly from the perspective of the entire protocol stack to see the simplification of NB (Mr. Wu defaults that you know that the physical layer is part of the protocol stack, not to expand).
Let's compare the traditional LTE and NB protocol stacks, and we can see how NB is determined to enter the aggressive mode (it's just one!):
â¶PHY physical layer: channel redesign, reducing the computational overhead of the basic channel. For example, the PHY layer cancels the channels such as PCFICH and PHICH, and the PUCCH and SRS are cancelled in the uplink. This issue has already been mentioned in the previous chapter. It is not repeated here. Please consciously review the NB-IOT Low Cost Sunflower Collection part2.
â· MAC layer: protocol stack optimization, reducing the overhead of the chip protocol stack processing flow. Here is the key point, because in the view of Teacher Wu, the role played by MAC in LTE is really important! For a chestnut, if the physical layer is the foundation of the house, then the MAC layer is the pillar of the house!
◢ Only single-process HARQ is supported (two points are mentioned: one is that there is still a HARQ retransmission mechanism in NB, and the other is that it supports up to eight processes in LTE, and NB only supports a single process. What do you mean? Explain data transmission In the middle, the terminal must wait until the NACK/ACK feedback is obtained! Pro, this completely overturns the basic idea of ​​multi-process simultaneous transmission in LTE to improve transmission rate and efficiency);
MAC The MAC layer uplink SR, SRS, and CQI reporting are not supported. Without CQI, the important AMC (Adaptive Modulation and Coding Technology) function in LTE is not basically equal to martial arts?
éž does not support non-competitive random access function;
â—¢Power control has no closed-loop power control, only open-loop power control (this is also normal, if closed-loop power control is used, the algorithm will be much more troublesome, and the scheduling signaling overhead will be large).
When I wrote here, as an old driver, I have to say NB you are a loser! The home of LTE is almost over for you!
â¸RLC layer: RLC UM is not supported (which means that VoLTE-like voice cannot be supported), TM mode (this means that the system message of TM originally in LTE must also go AM in NB);
â¹PDCP: The function of PDCP is simplified in a large area, and the functions such as the security mode and RoHC compression given in the original LTE are directly castrated. After being simplified, the function of PDCP in NB is weak enough to breathe, and it is not necessary to call it;
RRC At the RRC layer: no mobility management (this means å•¥? means that NB will not support handover); new design CP, UP scheme simplifies RRC signaling overhead (subsequent separate analysis); added PSM, eDRX and other functions Reduce power consumption (please refer to the small power section for explanation).
TIps:
Note that when Mr. Wu explained the protocol stacks of the above layers, the order of the listed layers is in accordance with the protocol stack structure. In fact, this order is a basic routine for us to understand the protocol stack, and we are learning any The recommended learning order for a communication protocol stack. With this in mind, you can also guess the follow-up routines when Teacher Wu is explaining the technical details of NB.
However, it is necessary to remind everyone that the NB's protocol stack is modified on the LTE protocol stack, and there is still a certain relationship between them. This is because the current development of LTE is very good and has formed. The complete industrial chain, standing on the shoulders of the giant LTE, is a great drop for the subsequent cost reduction of NB.
2 Factors affecting costs such as industry chain and operations
Regarding the cost issue, I think there are two other cost factors that need to be considered. One is the operator's network construction cost, and the other is the maturity of the industry chain.
â—¢ For the cost of network construction by operators, compared with LoRa, NB-IoT does not need to re-establish the network, and the radio and antenna are basically multiplexed. Take China Mobile as an example. There is a relatively wide frequency band in 900MHZ. Only a part of 2G frequency band needs to be cleared, so that NB-IoT can be deployed at the same time, even NB and LTE can be deployed at the same time. However, according to the analysis of Teacher Wu's "NB-IOT Low-cost Sunflower Collection Part1", the problem is not so simple. The specific network construction mode will be analyzed in detail later.
For the industry chain, the chip is at the core of the NB-IoT industry chain. Now almost all mainstream chip and module manufacturers have a clear NB-IoT support plan, which will create a better ecological chain. It is good for reducing costs. For example, Huawei's acquisition of the company's Neul chip is relatively early, there are test samples; Qualcomm's chips are released in the fourth quarter of 2016, and Qualcomm's chips are NB-IoT and eMTC dual-mode chips; Intel's chips will be in the fourth quarter of this year. The first batch of chips will be provided, and commercial chips will be released at the beginning of next year; MTK chips are also under development and will be released in the first half of next year; ZTE Micro and Datang's chips are also under development.
â—¢NB adopts OFDMA in the physical layer and SC-FDMA in the uplink, which is basically consistent with LTE. In addition, there are many in the frame structure that are "based on LTE." In addition, when you follow the three working modes of NB, you will see more clearly how NB shares the same fate with LTE. All in all, NB comes from LTE and inherits many LTE implementations, and NB is much more simplified than LTE, so this brings a lot of benefits to subsequent R&D costs and mass production costs.
Having said that, Mr. Wu uses the popular example to tell you the truth: the simple understanding is that NB wants to achieve the peak of life, all kinds of big money, all kinds of demand! Do you know if you have a second?
3 chip cost progress
Finally, on the issue of cost, quote some "famous aphorisms" (online reports):
Luke Ibbetson, head of R&D at Vodafone Group, said: "If the industry chain can't reduce the cost of a single module to less than two or three dollars and achieve large-scale application, the NB-IoT market will not be able to do it. We need to be extremely low from a global perspective. Costs embed the IoT module in the device."
Hu Houkun, president of Huawei, believes that to stimulate the large-scale development of NB-IoT, the cost of the communication module must be less than $5. If the cost falls below $1, it will lead to explosive growth.
Therefore, despite the broad prospects of the NB-IoT market, there is a price war behind the fiery. The cost of NB-IoT is extremely low, and the cost should be reduced to $1 for large-scale applications. Currently, the single connection module is still at $5. And this price gap makes enterprises have to consider the cost advantage when thinking about NB-IoT. Although operators are actively promoting, there is still a long way to go to finally realize the productization of technology.
As the great leader Chairman Mao said: the future is bright and the road is tortuous.
If it is realized, the friends can go and tell: Mom is worried about my kidney again!
4 Low-cost sunflower collection summary
Teacher Wu used three chapters to explain the low-cost problem of NB. The following is a summary of the three low-cost parts.
I have to say that in order to practice the Peking Confucius Sunflower Collection, NB has carried out the palace again and again from the whole body:
The physical layer and MAC on the protocol stack have been greatly simplified to reduce computing power;
æŠ Entering the aggressive mode on the hardware can save the province;
å‚ Try to make big money in the industry chain, and ask for it.
High efficient charging speed for Samsung laptop, stable current outlet can offer power for the laptop at the same time charge the laptop battery. The best choice for your replacement adapter. We can meet your specific requirement of the products, like label design. The plug type is US/UK/AU/EU. The material of this product is PC+ABS. All condition of our product is 100% brand new.
Our products built with input/output overvoltage protection, input/output overcurrent protection, over temperature protection, over power protection and short circuit protection. You can send more details of this product, so that we can offer best service to you!
Samsung Adapter,Charger For Samsung,Power Supply For Samsung,Laptop Charger For Samsung
Shenzhen Waweis Technology Co., Ltd. , https://www.huaweishiadapter.com