In data transmission, data collisions are a significant issue that must be addressed. This phenomenon can result in data loss, errors, or delays, ultimately affecting the normal operation of devices and the integrity of data. Data collisions differ from signal interference, which refers to the negative impact of external factors or other signal sources on ongoing wireless transmission signals. In contrast, data collisions specifically refer to situations where two or more devices transmit data simultaneously, causing interference at the receiver end.

Common techniques for managing collisions in wireless transmission include Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and Code Division Multiple Access (CDMA).

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a widely used method in wireless networks. Before transmitting data, a device listens to check if the channel is idle to avoid collisions. When the channel is idle, the device does not transmit immediately; instead, it waits for a random backoff time before sending data. If the channel becomes occupied during this waiting period, the device will wait again for a random time before trying to send data. Additionally, the Request to Send / Clear to Send (RTS/CTS) mechanism can further reduce the likelihood of collisions. The sending device first sends an RTS signal, and when the receiving device acknowledges with a CTS signal, other devices receiving the CTS signal know not to transmit data during that time, thus avoiding a collision.

This technique is widely used in Wi-Fi networks, where it effectively reduces data collisions and improves wireless network performance. For example, in a home network with multiple devices (e.g., smartphones, computers, smart appliances) that need to communicate with the wireless router simultaneously, the CSMA/CA mechanism helps coordinate their transmissions, ensuring more stable data transfer.

Time Division Multiple Access (TDMA) is a time-slot transmission method that divides the transmission time of a wireless channel into multiple time frames, each of which is further divided into time slots. Each device is allocated a specific time slot to transmit data, thereby avoiding collisions caused by simultaneous transmissions from different devices. This method can be compared to traffic lights on a road, where time is divided into different segments, and only specific vehicles are allowed to pass in each segment.

TDMA is used in wireless communication systems that require high real-time performance, such as the Global System for Mobile Communications (GSM) network. It ensures that each user (device) has exclusive access to the channel during its assigned time slot, providing high reliability in data transmission. However, one downside is that the channel utilization rate may be limited. If a device has no data to transmit during its assigned time slot, that time slot will go unused.

Frequency Division Multiple Access (FDMA) divides the total bandwidth of a wireless channel into several distinct frequency bands (sub-channels), each allocated to a specific device for data transmission. This approach allows different devices to operate on different frequency bands, much like dividing a wide river into different channels for boats (data) to travel without interfering with each other, thereby preventing data collisions.

The advantage of FDMA is that the technology is relatively simple, and signals on different frequency bands can transmit simultaneously without interference. However, the downside is that the spectrum utilization rate is relatively low, as there must be protective frequency bands between different channels to avoid interference.

Code Division Multiple Access (CDMA) assigns each device a unique code sequence. When transmitting data, the device encodes the data with this code sequence before sending it. At the receiver end, the original data can be recovered by decoding it using the same code sequence. The code sequences of different devices are orthogonal, meaning that even if multiple devices transmit data simultaneously, the receiver can distinguish between the signals using the unique code sequences, much like assigning each device a unique language. The receiver can then identify and interpret each language to extract the data sent by the corresponding device.

CDMA is widely used in modern mobile communication systems. It offers high spectral efficiency and strong interference resistance, allowing multiple users to communicate simultaneously. CDMA also excels in soft capacity, meaning that the number of users can be dynamically increased within a certain range without significantly degrading the communication quality.