Visible light communication (VLC) is a communication manner in which an electromagnetic wave within a range of a visible light frequency band is used as a transmission medium for communication. In recent years, the VLC communication has been attached with importance in academia and industry because of particularities of a frequency band used for the VLC (for example, (1) the VLC is in a relatively wide frequency spectrum from 430 THz to 750 THz, and this frequency band can be used without a license; (2) infrastructures are widely distributed; (3) the VLC is eco-friendly with no electromagnetic pollution; (4) the VLC is safe to human body; and (5) the VLC has a confidential security function because information transmission in the VLC has to be limited only at a location that can be illuminated by light).
Currently, in a VLC communication technology, there are the following problems in an uplink transmission process from a terminal (such as a smartphone or a tablet computer) to a VLC access point (AP): (1) user experience is poor because uplink transmission from the terminal to the VLC AP needs to be performed by a light emitting device of the terminal, and terminal use by a user is affected when the light emitting device is turned on; (2) power consumption is relatively large because when the light emitting device is turned on, power of the terminal needs to be consumed, and the power consumption of the terminal increases then; (3) a link may be blocked because an obstacle such as a wall or a door cannot be passed through during VLC transmission, and a range and a distance of the VLC transmission are limited; and (4) there is a hidden node in uplink transmission because transmission of light is directional. When a terminal performs uplink transmission to a VLC AP, another terminal in a coverage area of the VLC AP cannot detect the uplink transmission performed by the terminal, that is, the terminals are hidden nodes to each other. Therefore, when a current terminal is performing uplink transmission, if another terminal also sends data to the VLC AP, a collision occurs, thereby affecting network throughput.
To resolve the foregoing problems, it is proposed a heterogeneous network on which a VLC link is used for down transmission and an RF link is used for uplink transmission, for example, Wi-Fi, ZigBee, IR, Bluetooth, LTE, and GSM are used for uplink transmission. Replacing a VLC link with an RF link to perform uplink transmission can better avoid the foregoing problems in VLC uplink transmission, in an uplink transmission process of VLC MAC information (such as an acknowledgment (ACK) frame or a command frame). However, at a transmit end, a VLC media access control (MAC) layer needs to send, by using a primitive, the VLC MAC information to an adjacent higher layer first, and then, at a receive end, an adjacent higher layer needs to send, by using a primitive, the VLC MAC information to a VLC MAC layer. Interaction between adjacent protocol layers in a protocol stack needs to be implemented by using primitives, and each primitive has a fixed function. After a primitive is defined and prescribed in a standard, a primitive name, a primitive type, a primitive parameter, a primitive function, an occasion in which the primitive is generated, and an action after the primitive is received are in a one-to-one correspondence with the primitive. Among primitives that have been prescribed in the existing IEEE 802.15.7 standard, no primitive can implement the foregoing function of correctly exchanging, between a VLC MAC layer and an adjacent higher layer of the VLC MAC layer, an ACK frame and a command frame that are generated by the VLC MAC layer; therefore, according to the existing standard, when uplink transmission is performed on a heterogeneous network, a transmit end device cannot correctly and effectively send VLC MAC information to a receive end device by using another link.
USPTO Backgrounds
USPTO Backgrounds