# Bounce: A High Performance Satellite-Based Blockchain System
## 2 Related Work
### High Performance Blockchain Systems  
The two most important performance criteria for a blockchain are throughput (the number of transactions that can enter the blockchain per second) and response time (the time from when a client sends a transaction to the blockchain server to the time when the transaction is placed on the blockchain). Response time is important because consumers and businesses do not want to wait, e.g., for the completion of a credit card transaction. Throughput is important because a blockchain is most useful when many agents can use it concurrently, requiring a high rate of transactions per second.  
In an effort to increase transaction throughput and reduce block confirmation time, several approaches have been proposed and implemented. One goal is to achieve throughputs and response times at the level of the Visa payment system, which handles up to 65,000 transactions per second (tps) [39] with a confirmation time of less than a few seconds.  
When the Ethereum Merge [40] took place, Ethereum's consensus mechanism changed to Proof of Stake (PoS) from Proof of Work (PoW). With the update, transaction finality is no longer probabilistic but transaction response time could be as long as 6.4 min (32 slots \(\ast\) 12 s/slot). According to [PERSON], Ethereum can support up to 100,000 tps with the Merge. As of January 2025, Ethereum on average handles around 13 transactions per second [41].  
Solana [42] combines Proof of Stake with a hash-chaining concept called Proof of History to order transactions. Around every 400 ms, Solana produces a new block but it could still take up to 32 slots to finalize it, up to 13 s. As of October 2024, Solana handles up to 5200 transactions per second in production and will be able to handle up to 65,000 tps according to its benchmarks [43].  
Polkadot [44] employs a multi-chain architecture which enables parallel transaction processing to improve throughput [44]. It produces a block every 6 s, and it takes from 12 to 60 s for transactions to be finalized. It currently serves 1000 tps with plans to upgrade capacity to 100k tps.  
Avalanche [45] is composed of multiple blockchains, and uses a directed acyclic graph (DAG) structure to enable parallel processing of transactions. Blocks are produced every two seconds on Avalanche, and once one is produced it's final. Avalanche serves 10 transactions per second.  
Algorand [46] provides rapid finalization and high throughput using Byzantine Agreement. Validators are securely selected by verifiable random functions. Algorand producesa block every 2.85 s and can hold up to 25,000 transactions, which results in a throughput of over 10,000 transactions per second [47].  
Table 1 compares the throughputs and response times of the principal high performance blockchains including _Bounce_, whose throughput is roughly 100 times its nearest competitor.  
Thus, the main contributions of _Bounce_ compared to the state of the art are far lower energy expenditure than fully distributed protocols such as BitCoin, high throughput (in the millions of transactions per second), fault tolerance, and low response time. We will also show that the design is scalable, because the critical path consists of sending and validating arrays of Merkle roots. This enables throughput to increase further without increasing response time.